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Finding the best solution: water chemistry issues can baffle even veteran technicians. In this Q&A, service experts answer a variety of questions.

Water chemistry problems are frustrating. Things may be going along perfectly fine on a service technician's route, when suddenly, a murky stew appears where just recently sat a sparkling, clear pool.

Solving the problem typically requires some detective skills. These abilities include a good grasp of water chemistry, the proper use of various products, a little elbow grease and enough patience to follow through until the issue is truly resolved.

To get to the bottom of some of these issues, Pool & Spa News asked chemical manufacturers, pool and spa veterans, techs in the field and visitors to the magazine's online forum at to share some of the water-chemistry quandaries they've recently found themselves in or answering.

The questions that follow reflect the variety of problems a pool or spa may face. While some of these are basic issues that are always worth a second look, others speak to those rare circumstances that may occur from time to time. Regardless, the fixes should get the pool back on track and your customers back in the water.


Q I'm stumped. How can the pool's pH be low when the alkalinity level is high? What can I do about it?

Low pH and high alkalinity are often found when water from an aquifer is added to a pool. The pH may increase as the water comes to equilibrium and some of the carbon dioxide evaporates. If the conditions persist and the pH and total alkalinity are opposite of one another, always fix the low number first. In this case, add a pH increaser until the pH is within a normal range. Then adjust the total alkalinity by adding a pH level reducer.

Q If chlorine works better at lower pH readings, why not keep the pH lower than 7.2 to 7.6?

Chlorine does work better at a pH below 7.2. However, there are some consequences to keeping it low. As the pH falls below 7.2, chlorine can become increasingly aggressive and irritating. Corrosion can present a problem when the pH is below 7.0. Depending on the type of pool, corrosive low-pH conditions can cause surface etching, liner wrinkling and deterioration of the metals in pumps or heaters. A pH of 7.2 to 7.6 helps you assure bather comfort, allow for effective sanitizing and avoid corrosion.


Q How can I increase the efficacy of an algaecide?

In addition to properly dosing the water, try adding algaecide or sanitizer in the morning on a bright, sunny day. Algae grow in the presence of sunlight. Adding algaecide during the plants' peak growth period will increase their intake of the chemical, making the product more effective. Brushing the algae, especially black algae, at least once daily also will help expedite the removal. The sweeping process penetrates algae's protective coating, making the plants more vulnerable to the algaecide.

Q What is pink algae and how do I get rid of it?

Pink algae is not an algae at all, but a bacteria. Many normal algaecides will not reliably work on this. However, there are products designed to assist chlorine with the removal of this bacteria.

To eliminate pink algae, you must superchlorinate the pool. Turn off the filter and wash it with a good cleaner specifically made for filters. Let it soak overnight, then backwash this water to waste. Allow the chlorine levels to subside before your customers use the pool again. (Hint: Toss into the pool any equipment that is normally used for maintenance--such as hoses and brushes--prior to superchlorinating. These need to be disinfected, too.)

Q What about high phosphate concentrations? Can they cause algae blooms?

Sources of phosphate include fertilizer, which can drift in from local farms or lawn applications, and some metal-control and stain-removal products. Phosphate is a nutrient for algae, but it doesn't stop algaecides from eliminating or preventing algae.

Q How can I stop algae at the end of the swim season?

Using a preventive algaecide can reduce the presence of algae all season long. However, some pool pros find algae control is more difficult in late summer due to higher water temperatures and an increase in the amount of contaminants in the water. Overstabilization also may be a contributing factor. If trichlor is the primary sanitizer and dichlor shocks have been used, the cyanuric acid concentration in the water can build over the course of a summer. High concentrations of cyanuric acid may reduce the chlorine's ability to control algae (if chlorine is used alone).

The most practical option for reducing the cyanuric acid concentration is to drain part of the pool and refill with fresh water. Prevention is a much better choice. This can be achieved by balancing the use of stabilized and nonstabilized chlorine, so the cyanuric acid concentration is kept low.


Q Which factors contribute to chlorine demand?

Chlorine demand is caused by a combination of issues, including the buildup of organic items, such as plant debris and algae. It can also be triggered by organisms such as dead bugs and earthworms; swimmer contaminants, including sweat, suntan oils, cosmetics and lotions; and foreign chemicals such as fertilizers and cleaners that are washed into the pool.

Another contributor to chlorine demand is ammonia, which comes from swimmer waste, rain, pollution, source water, animal waste and especially fertilizers. Once in the water, ammonia consumes the killing agent (hypochlorous acid) to produce combined chlorine and an excessive chloramine accumulation--which can contribute to a demand situation.

Q How do I treat for a demand situation?

If the chlorine level is zero at any time, a demand may be present. There are test kits on the market that help estimate the chlorine demand. To prevent it, always maintain a chlorine residual and shock on a routine basis. Add extra shock product if a high combined chlorine level is present or after a big rain, heavy bather loads or the addition of fill water.

It's wise to sequester any metals before you shock or oxidize the chlorine demand; this will help prevent metals in the water from staining the surfaces. After you add the chlorine/shock, wait three hours and then check the residual. Continue this process until a residual is maintained overnight. Keep the water circulating to allow the treatment chemicals to mix throughout the water. Once the demand has been satisfied, chemically clean the filter to remove organic contaminants from it.

Also, if the pool is in a demand situation, your test kit may not accurately measure the cyanuric acid level. Satisfy the chlorine demand first, then test for cyanuric acid.

Q Will high nitrate concentrations increase chlorine demand or cause algae?

Nitrate alone won't cause chlorine demand because chlorine doesn't react with it. Though nitrate is an essential nutrient for algae, it doesn't keep algaecides such as chlorine, bromine or quats from killing the plant. Because plenty of other nutrients that algae love can be found in pool water, limiting these levels is more challenging than maintaining a chlorine residual.

High nitrate concentrations might be an indication that the water has accumulated a number of different contaminants, some of which could have a chlorine demand. If you're having trouble with algae or with maintaining a residual, partially drain and refill your water. Superchlorination or oxidation may help, but even chlorine doesn't destroy every pool water contaminant.

Q Some customers are wary of salt chlorine generators. How can I alleviate their concerns about corrosion?

It's not uncommon for customers to bring up questions about these generators and corrosion. They know, for instance, that salt is often used on the roads in winter, which can have a negative effect on cars. Car parts made of ferrous metals and other alloys can rust. However, as you know, the salt level in pools is kept much lower. In addition, pools aren't made of ferrous metals. The salt added to a salt-chlorinated pool will only result in corrosion if two dissimilar metals are in immediate proximity to one another.

Pump, filter and accessory manufacturers have long known about this problem, and the newer products are designed for it. In steel-wall pools, the liner separates the water from the metal. Gunite pools have finishes that are saltwater tolerant, and fiberglass pools are unaffected. However, if the ring on an underwater light is stainless steel and the screws that keep it fastened are chrome-plated brass, they will dissolve over time. The corrosion problem is solved if the screws are stainless steel. Of course, always be sure that the overall water chemistry is maintained within the accepted parameters, as with any pool.


Q Can simple household cleaners be used to remove the ring around the waterline?

It's strongly recommended that only a tile cleaner specifically designed for pools is used to remove this unsightly ring, which is most likely an accumulation of oils and dirt from swimmers, or possibly some scale formation. Household cleaners don't contain the needed balance of both oil/grease cutters and scale-dissolving ingredients.

In fact, household cleaners can cause foaming or dull a tile line due to the abrasives in their ingredients. Even worse, they may react with the pool's sanitizer. You may want to consider enzyme-based products, which are formulated to control grease and oil before they build up, to prevent the ring from appearing in the first place.

Q What are enzyme-based cleaners and how do they work?

Basically, enzymes are substances that accelerate chemical reactions. Enzyme-based cleaners are designed to assist in the process of breaking down oils and proteins. Enzymes break large particles into smaller ones, which can be handled more easily by a sanitizer. Regular enzyme use helps reduce scum-line buildup.


Q How should I treat stains coming out of the return inlets?

This kind of stain may indicate corrosion of metal parts in the circulation system, such as the heater. Before treating the stain, you should identify and address the cause. First, make sure the water is balanced according to the Langelier Saturation Index or the Association of Pool & Spa Professionals' recommendations for pH, alkalinity and hardness.

if the water is properly balanced, check other possible causes. Are acidic sanitizers such as trichlor being used in the skimmer? If the pump is shut off, these sanitizers can continue to dissolve, and this low pH solution can corrode the heater. Once the cause of the corrosion is corrected, the stain can be removed using a metal stain-removal product.

Q How should I treat clear green water in my customers' pools?

Metals are the typical culprits when the water has a clear green color. The most common cause in this case is dissolved metals such as copper, iron or manganese. Before treating this condition, you should first identify and address the cause.

Metals can enter the pool through fill water, especially if well water is used to counter evaporation. Check the fill water's metal concentrations with a metal test kit or strip. If metals are present, the pod needs to be treated routinely with a metal-control product.

Pools with copper plumbing or heaters are prone to having metal in the water due to small amounts of corrosion of these components. To avoid equipment deterioration, be sure the water is balanced according to APSP's recommendations (or your state/local health codes, if applicable).

Another possible cause of discolored water is the presence of dissolved organic compounds, typically from swimmer waste, dirt, leaves or grass clippings. If this is the cause, good filtration and shocking the pool should remove the color from the water.

Finally, pools can take on a clear green appearance during the early stages of algae growth. They should be treated immediately to prevent the problem from getting out of control.


Q What causes water mold and how do I get rid of it?

Water mold is caused by a common soil fungus, called Paecilomyces. Unlike algae, which require sunlight to grow, water mold can grow throughout the pool's circulation system. The mold appears as an off-white or pink slimy growth.

In pool water treated with polymeric biguanides, the organism contains an enzyme that rapidly eliminates the oxidizer (hydrogen peroxide) from the water. If slime deposits are coupled with a failure to maintain an oxidizer residual, the cause is likely to be a water mold problem. In addition, the water may become cloudy. Sometimes water mold infestations can reside within the plumbing and filter, and do not have an impact on water clarity.

Once water mold has been properly diagnosed in a biguanide pool, scrub accessible pool and pump surfaces and chemically clean the filter media. Then treat the pool with a product designed to oxidize fungus and mildew. Add a flocculant directly to the skimmer. This will help the filter capture any free-floating water mold. Lastly, boost the sanitizer level up to 50 ppm and add a double dose of oxidizer. Treatment and diagnosis in chlorinated pools will require the use of shock chlorination along with clarifying chemicals if the water is cloudy.

Q What's the best way to neutralize chemicals used in pool servicing that have been spilled in the backs of trucks?

Some techs attempt to use neutralizing chemicals or compounds to handle this situation. However, trying to neutralize a possible mixture of chemicals is probably too risky. You're better off using copious amounts of water to dilute and flush out all the chemicals. The water should reduce the risk of chemical reactions. Remember, chemical spills should always be handled in accordance with hazmat regulations, the product's Material Safety Data Sheet and/or the instructions provided on the packaging.

Q I heard there's a product you can add to the water that helps keep the pool temperature from dropping at night. Is that true?

Strange, but true. The product is designed to form a monomolecular layer on the pool surface. It's used in the evening, after the filter is turned off. Does it work? In theory, if you reduce evaporation, you will reduce heat loss.


When the water heats up, chemistry issues also can flare up. Between the higher temperatures and the smaller volumes, these hotbeds of activity can quickly turn into troublemakers.

That's why industry professionals keep close tabs on spas and the water issues they present.

Q How often should I recommend that my customers test their spa water? Everything I read seems to give a different answer.

There is a lot of subjectivity on this topic. Most feel it's better to test more often than less often. The sanitizer and pH levels should be checked prior to spa use. If the sanitizer level is too low, it should be adjusted and at least half an hour should pass before the spa is used. Also, tell customers to test the spa after each use. This enables the sanitizer to be replenished on an as-needed basis, decreasing the possibility of bacterial growth between uses.

If the spa is only used occasionally, it should be tested at least weekly, to ensure the sanitizer level is being adequately maintained. The proper balancing of spa water will, in the long run, avoid many problems.

Q How do I maintain correct pH in a spa?

Always add chemicals with the circulation on, but the air off. Employ aeration only when the spa is being used and, if possible, lower the spa temperature when it's not being used to combat pH increase. After the spa is used, the pH is usually high. Turn off the aeration, allow the spa to rebalance/ adjust for an hour, then check the pH and sanitizer levels and modify if necessary.

Q Can nonchlorine pool shocks be used in spas?

Most companies don't recommend it. Nonchlorine shocks for pools aren't buffered and may affect the spa's overall water chemical balance. It's best to use a nonchlorine shock designed specifically for spas. This helps reduce the need for any extra chemical treatment to keep the pH in the proper range. If you use a nonchlorine shock, make sure the spa maintains a sanitizer residual to prevent bacterial growth.

Q Products that lock in pH are supposed to be great for spas. So why does the water cloud up every time I use one?

You must be adding a liquid pH locking product. Liquid pH locking products should be used only in water that contains less than 150-ppm calcium hardness. Before adding it, test the water to ensure that the calcium level is below 150 ppm. If the water does get hazy, the filter will remove the cloudiness, but you should clean the cartridge after the water clears. Once the water clears, the spa will resume normal operation. Another solution is to use granular pH locking products. These are formulated for use in any calcium hardness range. Be sure to review the product's label for more information on using it effectively.

Q I've seen odd-shaped white chips on the bottom of some spas. Where's this stuff coming from?

Seeing these chips should warn you that the spa water may have been out of balance. The white chips are calcium deposits, or scale, that form on the heater elements. They are knocked off when the spa is running and will settle wherever they manage to travel to when the spa is off. This problem can be prevented by using a sequestering agent or scale inhibitor on a weekly basis to prevent calcium in the water from forming deposits.

Q My customer swears he never lets anyone use his spa without showering first. Yet he has problems with foam. What's going on?

You are right to first question what bathers may be introducing to the water in the way of soaps, detergents and cosmetics on their skin or suits. But another cause of foaming is soft water.

If the calcium level is low, below 150 ppm, you may see foam. This can be corrected by raising the calcium level to the 150- to 400 ppm range. Organic waste buildup also can cause foaming. By shocking the spa regularly, the wastes are oxidized and foaming is reduced.

Q Some spa owners think that if they have an ozonator, they don't need a sanitizer. How do I prove to them that this is false?

This has been an age-old struggle. Explain that ozone is a fast-acting oxidizer with a very brief efficacy period. Because of this, ozone doesn't necessarily kill everything in the spa water, particularly unwanted organisms floating in hard-to-reach parts of the spa system such as the interior plumbing. Therefore, a sanitizer with some staying power must be used to back up ozone. Less sanitizer will be required for ozonated spas than for spas without ozone, but some is required nonetheless so that a residual is maintained.

Q Ozone is said to be great for spas, but I'm dealing with one that's frequently cloudy. What's going on?

Ozone is an effective oxidizer and supplemental sanitizer. If an additional sanitizer isn't used, the water can become cloudy. Plus, this spa could be the victim of a myth that ozone renders clarifiers ineffective. Because of this misperception, some customers with ozonated spas do not consider using a clarifier. Ozone shouldn't affect the clarifying action. This is the case, in part, because one of ozone's key benefits--fast action--also means that only the water it contacts will be treated by it. Water passing through the equipment will not have the same benefit. So a clarifier will provide a very real benefit in an ozonated spa by helping the filter keep the water clean.
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Title Annotation:Close Up: chemicals
Author:Millunzi, Margi
Publication:Pool & Spa News
Date:Apr 25, 2005
Previous Article:In circulation: the last thing a commercial pool operator wants is downtime. Keep everyone in the water with these tips for submersible pump...
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