Why Using Salt Chlorinators in a Gunite Pool is Bad

How to Minimize Staining.

Staining of cementitious surface is a problem in traditional and salt water pools. These stains can develop almost immediately or over time. When stains develop gradually, the pool owners may not realize the problem until it’s too late.

Stains caused by leaves in the pool, metals in the source water, and exposed rebar will impact any type of pool. However, other causes of staining, such as galvanic corrosion and metals in the salt itself, are much more of an issue with salt water pools. Since salt water pools are unique, this article will address ways to help prevent stains in these systems.

Prime causes
The warning signs of staining in salt water pools include mild streaking down the sides of the pool, or discolored pool surfaces or water. Water discolorations can range from blue-green to dark brown. Interestingly, a significant contributor to staining can be the naturally occurring contaminants found in pool salt itself.

All salt molecules have the same chemical makeup — sodium chloride (NaCl). However, pool salt is not 100 percent pure sodium chloride; it contains different types and levels of impurities. Where the salt comes from and how it was produced — mined from underground salt deposits, mechanically evaporated, or evaporated from saline ponds (solar) — affects the levels and types of contaminants found. Manganese, iron and copper are responsible for the majority of staining issues.

The shape of the salt crystal is often an indicator of salt purity. Generally speaking, the more irregularly the salt crystal is shaped, the more impurities are either “locked” within the salt’s molecular structure or clinging to its surface. This is especially true of solar and mined salt, since these salts undergo little if any processing to remove naturally occurring contaminants.

On the other hand, some brands of mechanically evaporated salt are purer, having a more uniform, cubic shape. Mechanical evaporation involves solution mining and very high heat to produce salt from underground deposits. The high heat used to evaporate the salt actually eliminates many of the organic contaminants found in solar or mined salt.

Despite the additional processing it receives, some mechanically evaporated salt still contains high levels of stain-causing metals. Therefore, some manufacturers employ an additional purification step, called brine treatment, to remove these metals.

But even if high-purity pool salt is used, improperly applying it can also cause stains. If undissolved salt is allowed to remain on a cementitious pool surface, it can cause efflorescence, a type of staining. To put it simply, calcium carbonate is a major structural component of plaster, and it’s not very soluble in plain water; but high salt concentrations greatly increase its solubility.

In a salt water pool, the impact on plaster is minimal since the salt concentration is only about 3,200-3,500 ppm. However, the salt concentration in the immediate vicinity of an undissolved pile of salt on the pool floor could be well over 300,000 ppm. This concentration of salt is high enough to dissolve the calcium carbonate in the plaster, effectively weakening it.

In fact, the calcium carbonate quickly returns to its insoluble state as soon as it contacts pool water with “normal” concentrations of salt (i.e., 3,200-3,500 ppm). As the calcium carbonate falls out of solution, it attaches to and discolors surfaces. This discoloration is especially visible on colored plaster finishes.

Choose the right salt and add it properly
The greater the purity of the salt, the better it’s suited for use in a salt water pool. Ask your supplier to verify the manufacturing method and level of stain-causing metals in the salt you use — they should be able to guarantee its quality, or provide you with a product specification sheet showing the level of stain-causing minerals. Never use salt products not specifically designed for pool use, such as water conditioning pellets or rock salt. They contain more impurities, plus additives that should not be used in pools.

Even when using a high-grade pool salt, you should still follow best practices when adding it to the pool. For new pools, observe the 28-day waiting period before adding salt to ensure that the plaster cures properly. Then, add salt in the deep end — while the pump is running — and brush the salt until it is dissolved completely. In addition, consider adding a stain preventer when setting up a new salt water pool.

Test regularly
Staining due to metals in source water, corrosion of metallic equipment, or salt impurities is exacerbated by pH that is too high or too low. Weekly testing for pH and monthly testing for metals (if source water is high in stain-causing metals or if pools contain copper heaters) is recommended.

Treat when needed
There are many stain removal products available that can be used in salt water pools. Some of the more advanced salt products also contain anti-stain agents, and some manufacturers offer performance guarantees with them.

Avoid phosphorous-based stain-fighters, since they break down into orthophosphates, which are nutrients for algae and promote the formation of phosphate scale in the chlorine generator. Physically removing dissolved metals can usually be accomplished with sequestering agents and filter aids.

Fortunately, by following sound product application procedures and maintenance principles, stains can often be prevented. That way, customers can enjoy all the benefits of their salt pools without the worry of unsightly stains.

Source: Geoffery Brown- Pool and Spa News | 3.11.2011

Vinyl Pool Maintenance

Proper water balance will help maximize the life of vinyl swimming pool liners

Vinyl pool liners are protected by special additives and coatings that can withstand extremes of sun, temperature and constant exposure to chemically treated water. However, even the highest quality vinyl liner is subject to staining, wrinkling, shrinking or discoloration if the pool water is not balanced and treated correctly.

This type of damage to the liner is often associated with common missteps in maintenance. Here, we look at the signs and solutions to four different problem areas in maintaining vinyl liners.


The addition of a single chemical can damage a pool liner if the substance is not circulated sufficiently. Chemicals such as chlorine can settle in the deep end of the pool and bleach the liner if they are not allowed to circulate for several hours before a pool is closed for the season.

Spot bleaching of vinyl liners can also occur if undissolved particles of calcium hypochlorite or other slow-dissolving sanitizers are allowed to settle on the bottom of the pool. This can be prevented by pre-dissolving sanitizers in a bucket of pool water and adding the solution by pouring it through a sieve.

Using large, single doses of hydrochloric (muriatic) acid to adjust pH or total alkalinity levels can also damage liners. The acid then can chemically attack the liner’s printed pattern, since it is not sufficiently blended with pool water.

When a pool is closed for the season, professionals should install a winter cover that tightly seals around the perimeter. This will prevent the accumulation of leaves and insects during the winter months. This organic debris left on vinyl surfaces can cause staining and bleaching, and fungi that produces a pink stain on the vinyl.


Printed vinyl liners with base colors such as white, turquoise, light blue, grey and dark royal blue have excellent resistance to chlorine bleaching. Medium blue vinyl liners are, however, more susceptible to bleaching or loss of color if exposed to high concentrations of trichloroisocyanurate stabilized chlorine. This can happen in a period as short as 6 to 24 hours.

The immediate effects of other types of chlorine such as dichloroisocyanurate, calcium hypochlorite and sodium hypochlorite (liquid chlorine) are not as rapid or severe, as long as they are not mixed with other chemicals during or shortly after being added to the pool. Solutions of these types of chlorines can be applied directly to the liner for several hours to bleach out stains without adversely affecting the vinyl. If the concentrations of these types of chlorine are allowed to remain higher than the recommended levels of 5 ppm for superchlorination or 10 ppm for shocking for long periods of time, gradual bleaching of most blue liners will occur.

Be aware that certain combinations of pool chemicals at high concentrations can cause bleaching of vinyl liners.

Pool tar

Sticky substances, often referred to as “pool tar” or “pool goo,” can adhere and coat part of vinyl pool liners. This is sometimes caused by the interaction of quaternary ammonium compounds (quats) used in some algaecides and decaying organic material such as leaves, grass and insects.

Even chlorine can interact with quats to form a sticky material if both the chlorine and algaecide exceed the recommended levels. Quats can easily come into contact with high chlorine levels in automatic chlorinators, resulting in a gummy material being gradually fed into the pool, where it eventually precipitates on the liner.

Gummy material from the chlorinator can form when organic materials from cosmetics or tanning lotions are oxidized by high chlorine concentrations, resulting in a beige waxy substance.

Although it is not harmful to swimmers, sometimes a light coating of vinyl plasticizer material, which turns dark when contaminated with dirt, may rise to the surface of newly installed liners during the first idle period of winterization. This phenomenon is attributed to a lack of circulation, as it has never been observed in a pool that has been circulated over the winter. The material will almost always reabsorb in two to three weeks if the water is allowed to warm up (to over 21° C / 70°F) and circulate before being shocked with chlorine (at 6.0 ppm to 8.0 ppm) every other day.

Wrinkling and stretching

Vinyl increases dimensionally as it absorbs water, and wrinkles can develop even in properly-sized liners. The cause of this excessive water absorption is believed to be high levels of chlorine or bromine. If the sanitizer level is allowed to remain high, as much as five times the normal amount of water can be absorbed, which makes controlling water chemistry essential to maintaining the integrity of the liner.

Immersion testing of liner samples on chlorinated and brominated water in the 20 ppm to 50 ppm range shows that weight gains continue to climb indefinitely without leveling off, causing the size of the liner to increase by 1- to 3 percent.

To avoid stretching and wrinkling in vinyl liners, chlorine levels should not be allowed to remain higher than 3 ppm for an extended period, while bromine levels should not be allowed to exceed a maximum of 4 ppm.

Although peak chlorine levels of 5 ppm to 10 ppm are required for superchlorination, they should be allowed to return to the 2-3 ppm range by natural dissipation.

Controlling pH levels is also important in preventing wrinkling because pH affects sanitizer activity. A low pH of less than 7.0, for example, can cause a vinyl liner to discolor, wrinkle, stretch, lose tensile strength and increase in weight. A high pH level above 7.6 can lead to scaling or staining of the liner.

The information in this article is based on the strength of high quality, 100 percent virgin vinyl sheeting. Installers should always be aware of the quality of the vinyl being used in the pool liners they purchase, install and service.

Source: Rick Chaplin- Pool and Spa News | 1.15.2010

Vinyl Liner Pool Stains

Recognizing the vinyl-liner stains associated with various problems can inform sound diagnoses and effective solutions.

Protected by special additives and coatings, vinyl pool liners can withstand the extremes of sunshine, heat, cold and constant exposure to chemically treated water. However, even the highest quality vinyl liner is subject to staining if proper water balance is not maintained, or if debris is allowed to remain in the water.

The following technical information should help pool professionals avoid the black and pink stains that often plague vinyl liners — and deal with them when they arise.

Black staining

Black staining that appears on vinyl pool liners can originate from a number of sources, and primarily falls into two categories: metal staining and black algae. Depending on the type of stain, different treatments are required to correct the problem.

Copper, iron and manganese may be introduced into the pool via source water. They can form oxides in chlorinated pool water, and can precipitate out of solution, resulting in stains on the pool liner. These stains are generally black, brown or gray. Copper can also dissolve from copper or brass fittings in the plumbing when pool water pH conditions of less than 7 occur. This metal may also be present in some algaecides, though most now use copper in a chelated or complex form that remains in solution.

The presence of metal staining can be confirmed by treating a small portion of the stained area with a pH reducer to dissolve the metals. If the stain can be removed by this treatment, the staining is a result of metal deposits, and the remainder of the stains can be treated in a similar manner. If not, the stain is likely due to an organic source such as black algae (see below). If the staining is due to metals, the pool water may need to be treated with a metal treatment — such as a sequestering or chelating agent — once the staining has been removed, in order to prevent a reoccurrence.

Black algae appear as a series of small black spots on the pool liner. They are very tenacious organisms with a chlorine-resistant coating. First, brush the algae spots using a nylon brush to open up the algae coating. Next, test the pH of the water and reduce it to the lower limit of the normal operating range (7.2) to improve the effectiveness of the chlorine. Then, superchlorinate the pool and add a dose of a quaternary (“quat”) type algaecide. Make sure to follow the recommended dosage from the manufacturer, as excessive usage may result in foaming. Continue to brush the algae stains to maximize the penetration of the chemicals. Vacuum the dead algae to the drain once they have been killed.

Twenty-four hours after superchlorination, add a dose of a polymer algaecide (“polyquat”) as per the manufacturer’s recommendations. Polyquats are more expensive than regular quaternary algaecides, but they’re also more effective in controlling these resistant types of algae.

Once the staining has been removed, resume normal chlorination and water balance. Remember, the best protection against algae growth is a constantly held free chlorine level in the range of 1-3 ppm, a total alkalinity between 80 to 120 ppm, a pH between 7.2 to 7.6, and a calcium hardness of 200 to 300 ppm.

Another type of gray/black colored stain can occur when dye-producing microorganisms colonize the back side of a vinyl liner. The microbial dye becomes visible on the pool side of the liner as it wicks through the liner’s material, creating an irregularly shaped blotch. The stains on the pool side can be temporarily diminished through superchlorination, but they’ll reappear, since the source of the stain originates from the back side of the liner. Installation of a polyethylene barrier between the vinyl liner and the walls and floor of the pool can provide a barrier to these types of organisms.

Pink staining

Pink blotches that appear on liners are also likely caused by bacterial dye. Because the dye is highly soluble in the plasticizers used in flexible PVC pool liners, it can easily migrate through the liner.

The portion of the dye that is exposed on the surface can be bleached by chlorine; however, new dye will continue to migrate to the surface. The bacteria can become established on either the water side or back side of the liner. Growth on the water side may occur if free chlorine levels are allowed to drift below 1.5 ppm at the same time that organic matter and bacteria have accumulated in the water.

Superchlorination at this stage will rid the pool water of the contamination. But if the dye has penetrated below the surface, staining tends to linger indefinitely.

Growth on the back side may not take place directly on the liner, but rather on some other material in contact with the liner such as soil, or on a backing material like foam, felts or taping. Even though an anti-microbial agent is incorporated into the vinyl formulation, the dye can migrate from unprotected components and stain areas well beyond the point of infestation. If a lot of pink dye is visible on any backing material, it will very likely be the source of the problem.

If the liner is replaced, all contaminated materials must be removed and the entire pool shell (floor and walls) must be disinfected with a liquid chlorine spray or other suitable disinfectant.

Special problems are presented by locations that have high water tables, which continually bring water loaded with micro-organisms to the back side of the liner. Using disinfectants at these sites may be ineffective, since they will be quickly washed away. A possible defense may be some type of barrier layer; either a plastic sheet, perhaps polyethylene between the pool shell and liner, or a barrier coating of some kind applied directly to the pool shell.

Following the diagnosis techniques here, it’s often possible to head off vinyl stains before they spread, and possibly even to remove them — if they’re caught in time.

Source: Carl Flieler- Pool and Spa News | 11.25.2011

Lethal Light

Ultraviolet radiation can cleanly and rapidly destroy many organic contaminants — but it’s most useful when properly applied.


Between   the rising costs of electricity and growing consumer demand for “green” water   treatment solutions, ultraviolet (UV) radiation is becoming an increasingly   popular tool for disinfecting pools and spas.

However, like any sanitation technology, UV isn’t an end-all solution — its   effects are rapid but limited, and it often requires help from other types of   sanitizers.

Here, we talk with professional chemists about the exact nature of UV, the   means by which it sanitizes, and the most effective ways of implementing it.   A fuller, more detailed understanding of these principles will inform   decisions about where and how to apply UV for maximum effectiveness.

What is UV?
In the simplest terms, UV is a kind of light — to be more precise, it’s a   specific range of electromagnetic radiation wavelengths, most of which lie   outside the range visible by humans. While we can generally see light whose   wavelength falls between 390 and 750 nanometers (nm), UV’s wavelengths are   between 100 and 400 nm.

As with most artificial light, UV is produced by a bulb designed to generate   radiation in a specific range of wavelengths. “There are medium pressure and   low pressure UV lamps, and each one produces a different range of UV   wavelengths,” says Ellen Meyer, the Charleston, Tenn.-based tech service   manager for Lonza.

Shorter wavelengths indicate higher energy, and the UV range is subdivided   along a sort of energy scale, progressing from UVA (315 to 400 nm) to UVB   (280 to 315 nm) to UVC (200 to 280 nm) to high-energy radiation known as   vacuum UV (100 to 200 nm). Most UV radiation is at least somewhat effective   at killing microorganisms and breaking down organic compounds, but the   high-energy radiation of vacuum UV is the most powerful — and thus, the most   deadly to microbes. Still, even lower-energy UV is effective at deactivating   many organisms that resist the disinfection effects of chlorine.

Like other kinds of light, UV travels fast and doesn’t hang around — a   property that has its ups and downs. On the positive side, this means UV   reaches its entire target area almost instantly, and destroys the organic   contaminants it touches in a matter of seconds. The downside is, UV can’t   diffuse throughout the water the way, say, chlorine can — so its   effectiveness is limited to the path along which it’s projected, and it can’t   maintain a sanitizer residual in the pool.

Thus, some kind of additional sanitizer is a must in pools using UV. “Even in   Europe, where UV and UV-generated ozone are commonplace, additional chlorine   is required by health authorities,” says Corinne Lehr, assistant professor at   the California Polytechnic State University Department of Chemistry and   Biochemistry in San Luis Obispo, Calif.

Another significant concern in UV-sanitized pools is the replacement and   disposal of bulbs. “The bulbs have to be replaced every six to nine months,   and that costs $750 to $1500 every time,” says Jeff Jones, the Dallas-based   North American sales director of the residential pool division at Del Ozone.   In addition, Jones points out that the bulbs contain the chemical mercury,   whose disposal many cities regulate closely.

What does UV do?
Just as the sun’s UV rays can cause damage to our skin if we don’t wear   sunscreen, artificially generated UV can cause severe disruptions to the biochemistry   of microorganisms in pool water.

A predominant explanation for UV’s damage to microbes hinges on the damage   this radiation causes to DNA — the self-replicating molecule necessary for   life to reproduce. “Once an organism’s DNA is sufficiently damaged, that   organism can’t reproduce anymore,” Meyer explains. “So even if you were to   swallow some of the organism, it won’t be able to grow and reproduce and   cause an infection — you’ve pretty much disarmed it.”

But UV’s effects may also play more immediate roles in microbe destruction.   “Similarly to how UV gives us sunburns, it can cause physical damage to   microbes,” Lehr says. “But that damage can be even more serious to them — it   can kill them.”

The degree to which UV inactivates or kills an organism depends on multiple   factors, including the wavelength of the UV and the biological makeup of the   organism. The chart above details some kill and inactivation figures for   several common microorganisms under UVA radiation.

Along these same lines, UV can be used to destroy other organic contaminants,   like the chloramines that form when chlorine reacts with bather wastes in the   water. The only problem is, the molecular pieces of some chloramines stick   around in the water, and may re-form into their original compounds if they’re   not filtered out quickly enough — as can be seen in the charts to the right.

In the first chart, levels of monochloramine (NH2Cl) and nitrogen   trichloride (NCl3) are both lower after UV than before UV, but the   level of dichloramine (NHCl2) can sometimes be slightly higher. In   the second chart, it’s equally clear that even after a dose of UV, some of   the chloramines have re-formed, and their levels have actually risen. “So you   actually see more of certain disinfection byproducts with UV than you do   without it,” Meyer says.

How can UV be used effectively?
UV performs its work most powerfully when it’s used as a supplementary   disinfection system, supplementing other sanitation products such as   chlorine.

Some microorganisms, such as the notorious cryptosporidium, are highly   resistant to chlorine, because they produce hard shells known as cysts.   Others, such as black algae, produce slimy coats called biofilms, which also   can be tricky for chlorine to penetrate.

However, UV is often highly effective at breaking down these defenses. By   combining UV with chlorine, it’s possible to cut through the organisms’   protective layers and attack their vulnerable bodies and DNA — then oxidize   and destroy the remaining organic contaminants. This “one-two punch” can keep   even a large public pool free from infectious and otherwise annoying   invaders.

It’s also important to note than UV rays only attack organic matter in areas   they can directly reach — so if corners of the pool are “in shadow,” so to   speak, other disinfection methods will be necessary for keeping those areas   clear of algae and bacterial growth.

To ensure that the UV lamp is as effective as possible, it pays to examine   the shape of the pool carefully, and place the lamp in a location where its   rays will reach as many surfaces as possible. Another alternative is to   install an inline UV system, which bathes a closed chamber in UV light as   water continually flows through it.

Finally, it’s worth mentioning that UV won’t have an effect against metal   stains or phosphates — these issues will need to be treated with other   chemical solutions, such as sequestrants and phosphate removers. However, if   levels of these chemicals are kept within acceptable ranges, UV will prove a   powerful ally against any unwanted microbes that try to move in.

The bottom line is, there’s no end-all system for treating a pool — no   perfect solution that kills every organism in the water, produces no   disinfection byproducts, and operates in a way that’s completely safe and green.   Still, the highest priority is to keep swimmers free from infection and   irritation — even if the best way to do that is different for every pool. A   working understanding of how UV disinfection can fit into an overall   sanitation scheme will inform much clearer decisions about how best to apply   this technology.

Source: Ben Thomas- Pool and Spa News | 1.27.2012

Using Mineral Sanitizers

Ionic silver and copper can eliminate algae and bacteria while reducing chlorine demand

Silver is used as a powerful bactericide in many products, and copper is used as a common algaecide. As water contacts these minerals, positively charged ions are released; these destroy negatively charged contaminants. And that makes these particular minerals well-suited for use as supplemental sanitizers in residential swimming pools and portable spas.

Ions at work

Silver and copper are most effective in water in their ionic form. That means the molecules are independent from other compounds and carry a positive charge. These charged ions are attracted to negatively charged organics such as bacteria and algae. Once attached, these ionic elements destroy the organics by penetrating their cell walls.

Because the ions are unaffected by sunlight or heat, they can remain active in water for long periods. They are only removed by reacting with the organics or from splash-out. There must be a constant flow of these charged ions introduced to the water in order for this process to be effective.

Active and passive ionization
There are two types of devices manufactured today that accomplish this process — one using an active method and the other using a passive method.

Active-method devices create ionic silver and copper by applying a low-level direct current to electrodes that are plumbed into the filtration system. The electrodes, which are made from combinations of silver, copper and sometimes zinc, quickly release their ions into the water as they erode from electrolysis. The electrodes must be replaced periodically, and the water must be tested regularly to ensure the silver and copper levels do not rise to a point where staining could occur.

Sequestering agents are recommended with this method to prevent any possibility of staining. These devices were common in the 1980s and ‘90s, but they never reached mainstream status as sanitizers. Most pool professionals feel they were oversold as a total replacement to chlorine, or were installed and used improperly. Recent technology seems to take into account the lessons learned from the past, but ionizers are not what most people think of when mineral sanitizers are discussed.

Passive-method devices are usually what come to mind when discussing mineral sanitizers. They do not use any electricity, instead utilizing a flow-through cartridge containing a substrate that is coated with silver or impregnated with a combination of silver and copper. The substrate is made of small pebble-sized pieces that are retained in the plastic cartridge. The cartridge is then installed in a vessel that is plumbed into the pool’s filtration system. As the water passes over the substrate, silver ions or a combination of silver and copper ions are slowly released.

Sequestering agents are not necessary, since the ions are released so slowly. The cartridge contents will remain active for up to 6 months in pools and 4 months in portable spas. Passive devices are also a perfect complement to salt-water chlorinators. They do not interfere with chlorine generation, and many users find that they can turn the chlorine production rate down, making the electrolytic cell last longer. Passive devices are a preferred method of using copper and silver vs. adding them via a powder or liquid form, because those products usually are mixed with chemicals.

Safe sanitizers
The U.S. Environmental Protection Agency (EPA) plays an important role in the regulation of mineral sanitizers. While the copper and silver elements are considered safe, when an efficacy claim is made regarding algae or bacteria control, the EPA regulates its use. Therefore, make sure the product you use has an EPA registration number, lists the active ingredients, and shows all the cautions that the EPA requires. Though the EPA regulates and verifies the claims of mineral sanitizers, they do not regulate the product’s potential to stain or cause other problems. Look for products that are guaranteed to work and guaranteed not to stain the pool.

Benefits of mineral sanitizers

Neither the active nor passive methods eliminate the need for chlorine in a swimming pool, because minerals lack the ability to oxidize dead contaminants. Fortunately, the two biggest benefits of using minerals are a reduction in the amount of chlorine needed to maintain a residual, and the ability to maintain a lower residual. With a mineral sanitizer, you will notice at least some of the following:
• No more algae
• Fewer complaints about skin and eye irritations
• Fewer shock treatments required
• Fewer pH adjustments needed
• The TDS reading does not increase as quickly

The best testimonials for mineral sanitizers come from the pool professionals who use them. They report many benefits, such as getting rid of problem algae spots, lowering chlorine use, more consistent chlorine readings, and pools that stay sparkling clear with less work.
Source: Dan Kellog- Pool and Spa News | 8.13.2010

Starting Up a Salt Water Pool

Make sure saltwater pools are properly prepared for the beginning of swim season.

The initial steps in opening a saltwater pool are very similar to traditional pools, but a few key stages are critical to ensure the right start for the summer.

Get ready

First, for both types of pools, remove any plant debris that accumulated on the cover over the winter. Any plant matter that has made its way into the pool must also be removed. If water has collected on the cover, pump it off and away from the pool before removing.

Once the pool is clean, adjust the water level to about halfway up the skimmer face. You may need to add or remove water to reach this level, depending on your off-season climate and whether winterization was necessary. Connect the equipment, checking the pump and filter to make sure they are working properly, and turn it all on.

For saltwater pools, if you removed the electrolytic chlorine generator (ECG) during the off-season — particularly common in colder climates — put it back in place without turning it on. Pool water must have proper salt levels for the ECG to run correctly, so it shouldn’t be activated until after salt levels are checked and adjusted if needed.

Then run the pump for at least 24 hours to thoroughly circulate the water. This will help clear hazy water and filter out any remaining debris that found its way into the pool during the off-season.

Special salt steps

After preliminary opening tasks, startup steps for saltwater pools become more distinct.

For instance, saltwater pools must be shocked with chlorine. During the swim season, the ECG produces a constant amount of chlorine, so shocking a pool isn’t typically necessary. However, this fixed chlorine amount may not overcome the chlorine demand at startup that often is created by organic matter in the pool. A chlorine shock will solve this problem.

Before determining the pool’s salt level, take a water sample from a spot in the pool that is elbow-deep, away from the return lines, and test for and adjust pH, total alkalinity, calcium hardness and cyanuric acid. After the water is balanced, test for salt levels to ensure that the water has the appropriate amount for proper ECG function. The typical ideal salt level falls between 3,000- and 4,000 ppm, but instructions from the ECG manufacturer should be followed for optimum performance.

Run the ECG on its highest level of chlorine output for at least 24 hours to establish the proper amount of free chlorine. Once you’ve reached a level of free chlorine between 1- and 4 ppm, decrease the output according to manufacturer instructions to maintain the proper chlorine level throughout the season.

Benefits of salt water
Research shows that most traditional pool owners who have swam in a saltwater pool believe they deliver superior sensory benefits, and would prefer to own one over their existing vessel. The water created by a saltwater system is only about 1/10 the salinity of ocean water, so it feels softer and more soothing to the eyes, nose and skin.

Saltwater pools also can mean less maintenance. The ECG constantly converts salt water to chlorine, so chlorine levels are more consistent and there’s no need to purchase, transport, store, handle or frequently add chlorine.

Making the switch
If your customer has decided to switch to a saltwater pool, there are special steps needed for a smooth conversion. First, select the right-sized ECG according to pool size and bather load. If your customer has an
average-sized pool that is used heavily during the season, you may need to purchase an ECG that’s sized for a larger pool. This will ensure sufficient chlorine production for the pool’s actual usage.

Add treatment products to protect the pool against staining and scale as usual, but again, make sure these products are specifically designed for saltwater pools. The interior of the ECG has extreme pH ranges, high chlorine levels and relatively high temperatures. Many treatment products designed for traditionally sanitized pools break down into compounds like orthophosphates, which are nutrients for algae. The products used for salt systems should not contain ingredients like sulfates, or phosphorous-based sequestrants that can contribute to scale formation on cell plates.

Always use high-quality salt, especially when adding it to a customer’s pool for the first time. Commodity salt contains naturally occurring contaminants that can hurt your pool. Organic contaminants can cause scale, cloudy water and chlorine demand in the pool. Inorganic contaminants such as manganese, copper, iron, nitrates, silicates, sulfates, calcium and metals can affect water clarity, dissolution rate, and stain and scale potential. Check with your salt supplier to be sure of the type and source of the salt you are purchasing. Ultra-pure, mechanically evaporated salt is best for saltwater pools. Solar salt often has organic contaminants, and mined rock salt should never be used in pools.

When adding salt, use enough to reach the midpoint of the range recommended by the ECG manufacturer. It’s better to add too little salt than too much, as you can always add more; too much salt will require dilution with fresh water. Add salt to the deep end of the pool and brush until dissolved while the pump is running.
Saltwater pools require less maintenance than traditional pools, but they aren’t maintenance free. For residential pools, I recommend weekly testing for pH and chlorine, and monthly for total alkalinity, calcium hardness, stabilizer/cyanuric acid, metals and salinity levels to ensure they are maintained at the proper levels.

Source: Bob Harper- Pool and Spa News | 5.14.2010

Solving Stains

With an understanding of galvanic corrosion, stains in salt-chlorine pools don’t have to be a mystery.


Salt   chlorine pools have become popular over the past few years. There are no   hazardous chemicals on site, and water is sanitized and oxidized   automatically. Also, there are little to no chloramines. And many users of   salt generators claim softer-feeling water with less chemical odor and no dry   or irritated skin.

Yet   in spite of all these benefits, some have also reported strange phenomena.   These include discolored water and unusual stains that are hard to remove and   prevent.

Stains   appearing in salt pools include:
• Black flecks on pool bottom
• Black staining on ladders and light rings
• Reoccurring stains and discoloration on light rings around steps or rails,   and discolored water
• Purple haze and debris in pool water

While   these stains seem to be a mystery, typically they are a result of the high   TDS in salt pools and a simple chemical reaction known as galvanic corrosion.

To   understand this electro-chemical reaction, a simple grasp of the technology   of chlorine generators is first needed.

Salt   chlorine

Chlorine   generators work through a process known as electrolysis.

In   nature, chlorine is found primarily in the chloride ion, a component of salt   found in the earth or the oceans. Electrolysis is the means of generating   chemical products from their native state. A salt generator works by passing   electricity through a solution of sodium chloride to produce chlorine as a   disinfectant or sanitizer. The most commonly used chlorine generators are the   in-line type. In these systems, salt water is circulated over electrochemical   cells. The cells used in these systems typically are made of titanium, and   they convert the sodium chloride to free available chlorine. Now it’s   important to understand how this metal relates to galvanic corrosion.

Galvanic   corrosion
Galvanic corrosion occurs when dissimilar metals exist in a high TDS solution   such as a salt chlorine pool.

Some metals are nobler and more cathodic, meaning positive currents flow from   them. They also tend to steal electrons from the less noble anodic or   negative metals. A galvanic corrosion chart is used in industries that work   with fluids and metals, such as cooling towers. The chart shows that the   “anodic” or “less noble” metals at the negative end of the series — such as   magnesium, zinc and aluminum — are more likely to corrode than those at the   “cathodic” or “noble” end, which include gold and graphite.

There   are three things needed in order for galvanic corrosion to occur:
• Electrochemically dissimilar metals must be present
• These metals must be in electrical contact, and
• The metals must be exposed to an electrolyte (salt in solution)

In   a swimming pool, all three of these exist due to high TDS from the salt   content of the water. Most pools contain some copper in the system as well as   in the heat exchanger, or in any brass fittings or pipe that may be in the   hydraulics. As discussed earlier, the electrochemical cells in most chlorine   generators are made of titanium. Copper is a less noble metal than titanium,   and thus it corrodes as a result of the electrolysis in the high salt   solution.

This   electrolysis leaves black stains and debris in the pool. The copper also is   rendered insoluble in the water, which may create a green translucent color.

Solutions   to staining
The simple solution to this problem lies in finding a less noble metal to use   as a sacrificial anode that corrodes but doesn’t cause staining. Galvanic   corrosion occurs because, when these two metals are in salt water with an   electrical current, the weaker, less noble metal (copper) will corrode faster   than normal. Also, the stronger, more noble metal (titanium) will corrode   much slower than normal.

However,   the addition of zinc in these types of systems can prevent corrosion and stop   staining. Zinc is very low on the galvanic chart, and is one of the most   anodic metals found. In salt chlorine pools, zinc can be added as a solid   weight into the skimmer or attached in the circulation system. This slows or   stops the corrosion of copper. If the water is discolored from copper, it is   recommended to use a metal-removal product along with the zinc. This removes   the current discoloration and prevents reoccurrence. Most metal products on   the market tend to be phosphate-based, and this too can cause problems in a   salt chlorine generator. When selecting a metal product, make sure it’s   phosphate-free.

Another   mystery in both salt and regular pools is the occurrence of a strange purple   coloring and debris. This is due to high levels of cyanuric acid and   insoluble copper in the water. If pH and alkalinity drop too low, copper   cyanurate is formed, leaving a purple residue along the water line, and   around lights and steps. The solution here is to lower cyanuric acid down to   35ppm to 50ppm, and adjust up the alkalinity and pH. Also, the addition of   zinc will help keep copper from corroding into the water.

These   simple methods should help solve the mystery…and remove the stains.

Source: Terry Arko- Pool and Spa News | 8.14.2009

Servicing Salt Water Pools

Electrolytic chlorine generation can simplify some aspects of pool maintenance — but it requires adjustments in others.

If there’s one ingredient that most pool chemical regimens have in common, it’s chlorine. Almost since the beginning of the pool industry, service technicians across the country have been hauling around drums of the sanitizer, using test kits to monitor its concentration, and adjusting water chemistry to maximize its effectiveness.

But over the past decade, a growing number of pools have switched to a somewhat different system: Electrolytic chlorine generation. By using electricity to drive certain chemical reactions in salt water, electrolytic chlorine generators (ECGs) produce chlorine on-site.

Although the chemistry of an ECG-chlorinated pool bears many similarities with that of a traditionally chlorinated pool, it also involves some unique factors.

Here, through the expert advice of scientists and service techs, we examine these differences and provide some field-tested advice for servicing pools with ECGs.

Practical considerations

Perhaps the most obvious area in which ECG-chlorinated pools differ from traditionally chlorinated ones is in chemical transportation and storage. Because barrels of chlorine (or chemical compounds including chlorine) don’t need to be trucked to the site and stored there, many safety issues associated with these barrels — such as fumes and spills — are no longer major concerns.

However, the ECG itself adds some new tasks to the traditional maintenance regimen. Among the most important is keeping the salt cell clean. The chemical reactions involved in generating chlorine from salty water also contribute to the accumulation of calcium scale within the ECG — over time, this can lead to less efficient chlorine generation, or even equipment damage. Thus, it’s crucial to perform regular checks on the cell, and address any scale buildup with a light acid wash.

“The first year of a new ECG’s life, you can usually get away with cleaning the cell once every three or four months,” says Cliff Brummett, owner of CTB Pools LLC in Phoenix. But year by year, Brummett goes on to explain, the process of chlorine generation tends to drive the water’s calcium hardness and alkalinity upward, making more frequent cleanings necessary. “By the second year,” he says, “you typically have to start cleaning the cell every month.”

Salt water, and the process of electrolysis, can also contribute to certain kinds of degradation, such as galvanic corrosion. In fact, says Alison Osinski, Ph.D., principal-owner of Aquatic Consulting Services in Avalon, Catalina Island, Calif., “Some manufacturers may say their components were not NSF tested in salt water pools, and therefore [using them in a salt water pool] voids the warranty.”

This is especially a concern for small components in heaters, such as gaskets and O-rings. “You’ll need to pay more attention to those components, and replace them more often than you would in a traditionally chlorinated pool,” Osinski says. Weekly checkups of these components, and replacements of any that are beginning to show signs of damage, will go a long way toward keeping the equipment trouble-free.

Another consideration, which might seem obvious but is often neglected, is the fact that the system’s pump must be running in order for the ECG to produce chlorine. “Since pumps on residential pools usually don’t run 24 hours a day, we can get problems with these residential systems that we don’t see with commercial systems, because they don’t circulate the water enough,” Osinski says. Thus, it’s important to be sure the system is generating enough chlorine to maintain a proper residual in the time it takes the pump to run through one daily cycle.

Balance concerns
When it comes to the chemistry of ECG-chlorinated pools, most of the acceptable ranges specified by organizations like the Association of Pool & Spa Professionals and the Independent Pool and Spa Service Association will still apply — in other words, the water’s calcium hardness, total alkalinity, pH and temperature should be maintained in the same ranges as they would for a traditionally chlorinated pool.

However, there’s one important respect in which ECG-chlorinated water differs: its level of total dissolved solids (TDS). Whereas most traditional recommendations place the ideal range for TDS at approximately 300 to 1,800 ppm, salt water often contains 3,400 ppm of TDS due to the salt alone — in addition to as much as 1,000 ppm of other miscellaneous TDS.

ECG manufacturers typically specify an ideal range of salinity for pools using their devices — so it’s important to check the salinity of the water at least once a month. When performing these checks, be sure to use a test method that measures the salinity level in particular; not just the overall TDS — test kit instructions will specify which parameter each test addresses.

“A standard TDS test is going to measure all the salt, plus any other dissolved solids,” explains Ray Denkewicz, worldwide product manager for sanitization and chemical automation at Hayward Industries in North Kingstown, R.I. “So you might get a reading of 5,000 ppm, when in fact the salt contribution to that may be 3,000.”

Thus, distinguishing between these two types of TDS contributions is critical for maintaining balanced water. And an effective way to get a clear sense of the pool’s non-salt TDS is to perform a TDS test when adding salt to the pool for the first time. “That’s your starting TDS,” says Geoffrey Brown, developmental scientist at Pristiva Inc. in Overland Park, Kan. “Once your TDS increases 1,500 ppm above that, then you should start thinking about draining some of the water and replacing it with fresh water.”

ECGs’ tendency to drive pH and total alkalinity upward can impact other chemical parameters as well. “Not only can high pH result in bather discomfort, it also makes the chlorine less effective,” Brown says. This means that while a chlorine test might show that the water’s chlorine level is acceptable, if the water’s pH is too high, that chlorine will exist in a much less effective chemical form. Thus, weekly pH checks are essential for effective sanitation.

In these high-pH conditions, some say they’ve found that higher TDS creates a greater potential for calcium carbonate and other soluble calcium compounds to form scale deposits on surfaces throughout the pool and equipment. “The calcium will want to precipitate out of solution,” Osinski explains. “It can start clogging the pipes up, creating milky water, and causing scale.”

However, other scientists point out that a higher TDS would actually lead to more corrosive water, by lowering the water’s Langelier Saturation Index (LSI) value. “Higher TDS makes the water more corrosive,” says Karen Rigsby, leader of technical services at BioLab Inc. in Lawrenceville, Ga. “It’s inside the chlorine generator where you get the likelihood of scale formation, and that’s because of the high pH inside there.”

If calcium scale does become a problem in an ECG-chlorinated pool, experts say it’s generally reasonable to adjust the pH slightly downward with muriatic acid. Still, it’s a smart idea to calculate the water’s LSI value on every visit to the site, and visually inspect surfaces for any signs of corrosion, as well as calcium deposits.

Additive interactions
Even if the pool’s water has been balanced into an ideal LSI range, it’s still helpful to be aware of some additional chemical traits of ECG-chlorinated pools. Aside from their higher salt-contributed TDS, the other main chemical distinction of these pools is how their cyanuric acid (CYA) concentration must be managed.

As many service techs know, CYA is a chemical that protects chlorine from breaking down under the sun’s ultraviolet (UV) rays. Many traditionally chlorinated pools are chlorinated with trichlor tablets, which contain both chlorine and CYA. However, the chlorine in ECG-chlorinated pools must also be protected with cyanuric acid (CYA) — industry organizations like the APSP recommend an ideal range of 30 to 50 ppm — which means it’ll be necessary to add this chemical manually from time to time. Techs say approximately once per year is usually sufficient, but it still pays to test the pool’s CYA concentration every month to ensure that the level hasn’t dropped due to splash-out or backwash.

“But CYA doesn’t degrade,” Rigsby says. “It’s not something you have to replace all the time, but you want to keep an eye on it.”

Some service techs even recommend switching to tablets during colder months, when certain ECG models automatically shut down. “We use tabs during the winter, because our water gets colder than 55 degrees, and most cells shut off at 55,” Brummett says. This can help prevent algae blooms and other microbe infestations during the winter.

Trichlor tablets contrast with ECG chlorination in another way, too — while these tablets tend to drive the water’s pH downward, the pH of an ECG-chlorinated pool tends to drift upward (as discussed in the “Balance concerns” section earlier). This means the water balance regimen that keeps traditionally chlorinated pools balanced can send an ECG-chlorinated pool’s LSI value well above the acceptable range.

Sequestrants can lead to a few problems in ECG-chlorinated pools. Some simply aren’t as stable in the presence of high levels of chlorine — in other words, the levels inside the ECG itself — which can make them less effective. Also, some sequestrants are based on phosphates, which break down into orthophosphates — chemicals that combine readily with calcium in the pool to form calcium phosphate on the ECG. In any case, many manufacturers make sequestrants that are designed specifically for use in ECG-chlorinated pools; the packaging will usually specify this.

Some dry acids — such as sodium bisulfate — can leave sulfates in the pool, and these can contribute to scale problems similar to those caused by phosphate-based sequestrants. “And if you’re unlucky enough to live in a part of the country where you’ve got barium in the source water, then you can get barium sulfate in the ECG, and that is next to impossible to get off,” Brown adds. Pool test kits don’t generally include a test for barium; the best way to find out if it’s in the local source water is to consult the municipal water authority.

Bromine may also contribute to ECG trouble. Though this chemical can be a helpful supplemental algaecide in traditionally chlorinated pools.

“But you don’t want to use it in a salt chlorinated pool,” Denkewicz says, “because the bromide ions interact adversely with the electrodes in the cell.”

As the ECG’s electrodes make chlorine from chloride ions, they’ll also make bromine from bromide ions. “Bromide is harsh on the sensitive electrode,” Denkewicz explains; “it can damage it, and decrease the overall lifetime of the cell.”

Though these potential issues can cause problems for ECG-chlorinated pools, keeping them in mind will help ensure that many pitfalls associated with ECGs are avoided. As many ECG experts point out, chlorine is chlorine, no matter how or where it’s generated and introduced into the pool — but even so, a proper understanding of issues unique to ECG-chlorinated pools can extend the life of both the pool and its equipment.

Source: Ben Thomas- Pool and Spa News | 12.30.2011

Repairing Vinyl Liners

Experts share field-tested techniques for installing and repairing vinyl liners.


Vinyl liners are becoming more advanced every year. From plasticizers to UV inhibiters to thousands of color combinations, the options available to the builder and customer are nearly endless.

But even the newest liners are vulnerable to the same old issues, such as staining and punctures. Wrinkles seem to have a way of sneaking up from behind, and shrinkage can cause flotation in almost any climate. All these problems, however, have straightforward solutions.

Here, experienced pros reveal their secrets for mastering the art and science of vinyl, from installations to repairs.

Choose walls without foam
Vinyl liners are most durable when resting directly against metal wall panels. A layer of rolled foam backing puts the vinyl at risk for punctures and wrinkling, no matter what substrate it covers.

“Foam walls exacerbate liner puncturing,” says Michael Giovanone, president of Concord Pools and Spas in Latham, N.Y., a Pool & Spa News Top Builder.

Giovanone also points out that the weaker construction of a rolled foam layer lacks the holding power to keep a liner in place. “Foam lets liners creep and wrinkle,” he says, “because it doesn’t have a solid bond to the substrate or the wall.”

Imagine a piece of paper pressed against a hard surface, like a desktop; then imagine poking that paper with a sharp pencil. It’s nearly impossible to puncture the paper as long as it remains flush with the hard
surface. But lay that same piece of paper against a soft pillow, and any sharp object can rip right through it.

In short, a liner is only as strong as its weakest layer of backing.

“The backing behind a liner is the most important factor in that liner’s durability,” Giovanone says. “And the worst enemy of vinyl liners is wall foam.”

Measure and mark the liner
Fitting a liner’s beading onto the bead track can be a frustrating process. Manufacturers typically include markings on the liner’s underside to indicate its corners and center, and these can help a crew properly place the liner in the pool. But the manufacturer’s markings aren’t much help for aligning the top of the beading with the track.

“The manufacturer’s marks — the arrows — are just a rough approximation,” says John Warner, president of Done Right Pools and Spas in East Greenbush, N.Y. “And the manufacturer doesn’t put anything at the top of the bead.”

Warner, however, recommends a technique for ensuring the alignment is on target: Before unfolding a liner, measure it. Find the points where the top of the beading will actually line up with the corners of the bead track, and mark each of those alignment points on the liner’s underside.

“When I first open the liner up,” Warner explains, “I physically locate what I think is the exact spot where it’s going to line up with the corner at the top of the bead, and I make a little pencil mark at that spot on the back of the liner.”

Rethink sealing and vacuuming

During the initial installation, most crews hold the edge of the liner against the walls with duct tape or sandbags. But it’s not always possible to create a perfect seal this way. Wind, cold and dryness can quickly begin to stretch the seals, or even loosen the liner’s edges.

One possibility is to try a different approach right from the start. “Instead of duct tape,” Giovanone says, “use caulk to seal every [wall] panel before it gets bolted together.” Though this process takes more time, it creates a hardened seal that’s much less vulnerable to the elements.

Next, run the liner’s beading through the entire track. The usual practice at this point would be to leave part of the beading out of the track and tape an industrial vacuum pump behind the liner to tighten it. Giovanone says, “That’s completely wrong.” Instead, fit a vacuum pump over the top of the skimmer opening. As long as their dimensions are compatible, they’ll form a perfect seal.

“Liner vacs are manufactured to be square, and they’re meant to sit on top of the skimmer,” Giovanone explains. “It fits like a glove; you don’t need to use any tape.”

Because this scheme uses the vacuum’s shape and weight to secure the seal, it ensures a much tighter fit between the vacuum and the liner, and thus lowers the chance of wrinkles. When combined with the technique of caulking wall panels, it also avoids other taping-related issues, such as flotation.

“If you bead the liner and caulk your wall panels,” Giovanone says, “you will totally eliminate floating liners.”

Use only vinyl duct tape
If using duct tape on the liner is unavoidable, pick a brand made from vinyl. Many types of duct tape are made with cloth, which is an organic substance, and thus home to microorganisms that can quickly stain and degrade a vinyl liner.

“Pink and purple staining, which is a huge problem with vinyl liners, is actually the excretions from microorganisms,” Giovanone says. “It’s called microbiological staining, and it comes up through the
vinyl from the back.”

While shocking the pool will dissipate the appearance of the problem, this is only a temporary solution. Until the infection is totally destroyed, pink stains will continue to creep back through the liner.

The easiest way to avoid this issue is simply to avoid organic duct tape. Vinyl-based tape is inorganic, so it poses no threat to the liner.

Start filling as soon as possible
Because vinyl liners are designed to stretch to their full size under the weight of water, they’re most vulnerable to shrinkage immediately after installation, before the pool has been filled. Unless several inches of water are holding it in place, a liner may begin to shrink and float within 2 to 3 hours, even if a vacuum pump is pulling it tight.

“I’ve found that the old system of leaving the vac on, then pumping in water from the customer’s hose just doesn’t produce consistent results,” Warner says.

Instead of waiting for the hose to fill the pool, one option is to bring in about 9,000 gallons of water as your crew is finishing the installation. Once the liner’s wrinkles are brushed out and the vacuum pump is running, dump in enough water to fill the shallow end to a depth of about 6 inches.

“I always insist on it,” Warner says. “We have the water on hand as soon as installation is finished, and we dump it in the pool right away.” This prevents any shrinkage from taking hold during the first night, while the pool is being filled. Warner says this strategy is especially useful on colder nights, when liners are prone to shrinkage.

Though having water delivered does add an expense to the installation process, the benefits down the road will be well worth the initial cost. “It’s a money-saver for the customer in the long run,” Warner explains, “because the liner’s going to fit right, so it’s going to last longer.”

Hold onto that water
Groundwater seepage and shell uplift are major problems in areas with high water tables. Because vinyl pools require at least 6 inches of overdig, their sites are particularly susceptible to these issues. Hydrostatic relief valves aren’t always available to offset this danger, and the usual practice of pouring drained water onto the lawn only adds to the problem.

Fred Martin, president of Martin Pool and Spa in Pittsfield, Mass., has discovered a straightforward way to save money and prevent uplift at the same time. When draining a pool for repairs, instead of directing the flow of water to a deck drain (or the customer’s lawn), his techs pump all the drained water into tanks.

“When we go in to replace a vinyl liner,” Martin says, “we first set up some tanks to hold all the water we drain from the pool. That gives us a buildup of supply.”

When they’ve finished repairing or replacing the liner, the techs immediately return the stored water to the pool. This puts pressure back on the water table right away, and prevents the liner from floating while the pool is being refilled. It’s friendly to the environment, too.

“This way,” Martin explains, “you’re not wasting water, and you’re also making sure that if you’ve got ground water, it’s not going to come up through the sand or gunite.”

Source: Ben Thomas- Pool and Spa News | 6.25.2010

Pool Staining

While a lot of swimming pool stains are the work of familiar culprits, many have uncommon causes

Most pool owners assess the well being of their swimming pool by what they can see: the clarity of the water and the appearance of its surfaces. As a service technician, you must be able to diagnose problems that can compromise the homeowners’ visual evaluation of their vessel. There are many common issues that lead to staining in pools, and a few not-so-well-known offenders.

Water balance

Most stains and discoloration can be traced to improperly balanced water. But even “perfectly balanced” pools have the potential to contribute to these types of problems due to the almost-daily influx of metals, minerals and other contaminants. Oxidation also is a concern.

Common organic staining scenarios

Staining and discoloration can be broken down into two main categories: organic and inorganic. Common organic causes include scale, algae, “pink slime,” white water mold and vinyl liner mold. The Langelier Saturation Index measures the corrosiveness and neutrality, or scaling ability, of water. Water, by nature, “wants” to be neutral or balanced. When pH and/or total alkalinity are high, water cannot rid itself of either of these two important components, but it can push out calcium. Scaling is one unwanted by-product of this reaction.

When heavy rains combine with hot weather and low or no sanitizer, algae in its many forms can become an issue. Mustard algae seems to vanish easily when brushed, but will reappear quickly and continue to spread if left unchecked. Black algae creates a protective gelatinous coating. It also has roots, which can penetrate a pool’s plaster, fiberglass or vinyl surfaces. Green algae can first appear as a tinting of the water, which can rapidly transform a pool into a veritable swamp if not treated. In addition to a discoloration of the water, green algae also can produce rapidly spreading stains throughout a vessel.

Pink slime actually is reddish bacteria that most of us have seen on our showerheads. It can be introduced by rain, soil and contaminated swimsuits — as can mustard algae — and can rapidly grow in circulation pipes. Like pink slime, white water mold grows in circulation piping. This contaminant resembles small floating pieces of white tissue by the time it finds its way to the pool water. Although not a surface stain, vinyl liner mold is a fungus that grows underneath a vinyl liner, which is visible as a shadow beneath its surface. Tannins, commonly associated with trees, also can find their way into pools and create staining.

Common inorganic stains and discoloration
Inorganic troublemakers include scum-line buildup, cloudy or tinted water and iron and copper stains. When suntan lotions, body oils, make-up and dirt gather at the waterline, an unsightly scum-line buildup can occur. It should be noted that organic contaminants also can contribute, though they aren’t the main culprits. If left unchecked, additional dirt and contaminants will more easily adhere to an existing scum line, creating a snowball effect.

Cloudy water is a byproduct of unbalanced water, poor circulation and poor filtration. Ironically, the response of then adding too much clarifier can worsen existing cloudiness.

Metals such as iron, copper and manganese can produce a tinting of pool water and serve as a warning of sorts that metals are present in the system. All it may take is a shock treatment to plate the metals from the water onto a pool’s surface, thus creating a metal stain. Metal stains can also potentially be introduced from well and municipal water, metallic equipment parts, pool chemicals such copper- and silver-based algaecides, certain grades of salt for chlorine generators, certain grades of chlorine, ionizers, lawn chemicals and more.

Lesser-known causes of staining

Copper cyanurate, dubbed “purple haze,” can occur when a high stabilizer level (above 100 ppm) combines with copper, creating a purple precipitant. This purple stain is bright and highly visible, often showing up on tile, spillways and pool cleaners. If left untreated, copper cyanurate eventually will adhere to all pool surfaces. Until the stabilizer level is lowered to below 70 ppm, the problem can appear to be chronic.

Another potential stain-causer: potassium permanganate. If a house’s water supply is high in iron, manganese or hydrogen sulfide, many homeowners choose an iron/hydrogen sulfide reduction filter for their water treatment system. This filter contains manganese green sand, which reduces contaminants through an oxidation/filtration process. Should green sand water mix with make-up water, it can contribute to staining. The manganese in the filter is expelled when the system recycles, and it will create a pink/purple potassium permanganate stain when it comes in contact with the pool finish.

Iron and scale are two common causes of staining in a pool, but occasionally they work together to create a more obscure form of discoloration. This hybrid stain, known as iron scale, can be particularly difficult to remove, as standard treatment doesn’t often work. The only way to alleviate this buildup of layers is to remove first the top layer of scale, then treat the iron stain that it previously covered.
Source: Jack Beane- Pool and Spa News | 4.15.2010