Chemical Problems and Solutions

Chemical Problems and Solutions

Chemical Problems

Many pool water and surface issues can be handled by the pool owner. The Pool Care Troubleshooting Guide provides solutions to some common pool issues. Proper water chemistry is key to a properly balanced pool.

Troubleshooting Guide
Troubleshooting Guide

Often, many water and surface problems can be handled by the individual pool owner. The information below provides solutions to some common pool issues. Always make sure the water is properly balanced prior to any addition of corrective chemicals.

Read more on Algae Maintenance.

Total Alkalinity
Total Alkalinity

Total alkalinity refers to the ability of the pool water to resist a change in pH. The key purpose total alkalinity serves is to help control the pH in the pool. It does this by acting as a buffer so that when materials are added to a pool that would otherwise cause the pH to go up or down, these changes are managed and do not result in severe changes to pool water balance.

When a substance is added to pool water that could affect the pH, total alkalinity will react to neutralize it and help keep the pH in the desired range. Total alkalinity does not determine what the pH will be, but rather acts to help keep the pH in the range desired.

Total alkalinity is measured in parts per million (ppm) using a total alkalinity test kit. It is best kept in the range of 80-120 ppm. When the total alkalinity value is less than 80 ppm, the water can become aggressive and the pH can swing easily upward and downward and back again. If the value is higher than 120 ppm the water can become cloudy and scale forming and the pH will tend to drift upward.

In adjusting total alkalinity downward, the same acids used to lower pH are employed.  When reducing total alkalinity, it is best to add small amounts of acid, either liquid or dry, over a period of several days as opposed to making large adjustments rapidly. Adding too much acid at once may result in lowering the pH so severely that corrosion of pool surfaces and equipment may result. When raising total alkalinity, alkalinity increaser is the chemical of choice.  Adding the required amount in recommended increments over a few hours with the pool circulating is suggested.  Please be aware that some clouding could occur.


On occasion it is possible, especially in freshly filled pools, to find that both total alkalinity and pH need to be adjusted. Typically, if one factor is high or low, the other will be as well. It is not unusual, however, to have a condition where one factor is high and the other is very low. In such a situation, adjusting the wrong factor first may cause a significant problem with the other, or worse - cause a problem such as corrosion of equipment or precipitation of calcium. If this occurs with a freshly filled pool, it may be worthwhile to wait about 24 hours before making any adjustments. This wait will generally result in some natural balancing of the water without added chemicals. This process is commonly referred to as allowing the water to come into equilibrium. If additional adjustment is still needed, it will require far less time or chemicals.

In cases where the pH is low and the total alkalinity is high, raise the pH first into the normal range of 7.2 - 7.8 and then lower the total alkalinity. When the total alkalinity is low and the pH high, raise the total alkalinity first and then reduce the pH.

In all cases, never add acid to the pool water if the pH is less than 7.2, even if the total alkalinity is high. Instead wait for the pH to rise first before proceeding. If the pH does not come up by itself after a day or two you will need to add some pH Up before proceeding.

What is alkalinity?

All About Algae
All About Algae

Algae growth is perhaps the most obvious sign of something gone wrong with pool maintenance. Proper maintenance will not only keep your water looking great, but also allow for easy prevention of algae growth.

There are two basic groups of algae:

Black algae is the common name or term given to the dark blue-green algae found growing on pool surfaces. Black algae grows in localized areas such as along one wall, in the deep end, in a corner or around obstacles such as steps indicates an area of poor circulation and poor sanitization.

  1. Free-floating types including green and mustard varieties. These tend to be found throughout the water. Mustard algae tends to cling loosely to the walls of the pool and brushes off easily.  It tends to have a yellowish color.  Green algae will be visible throughout the water itself and will turn the water different shades of green depending on the infestation.
  2. Black algae is the common name or term given to the dark blue-green algae found growing on pool surfaces. Black algae grows in localized areas such as along one wall, in the deep end, in a corner or around obstacles such as steps indicates an area of poor circulation and poor sanitization.

The growth of both types of algae can be easily prevented by using a quality algaecide as part of a regular maintenance program, and by proper circulation. It takes far less algaecide to prevent algae growth from getting started than it will to cure it once it has occurred.

The regular use of algaecide is also recommended to prevent problems should a failure of the sanitization program occur. Due to the unique nature of chlorine or bromine, these residuals can often be lost very quickly in pools due to equipment or operator error or by heavy rainfall or bather waste demand.  Improper water balance will contribute to the ability of your sanitizer to work properly and prevent algae growth.  If this occurs without an algaecide present, the rapid growth of algae can occur in a few hours. However, if an algaecide is present, it will act as algae growth prevention (look at it as an insurance program) until the sanitizer system is functioning normally.

In spite of your best efforts, algae problems can occur and require some consideration for proper treatment. When an algaecide becomes necessary, the following factors need to be considered before treatment:

Amount of algae present

It is critical that sufficient algaecide is added to treat all of the algae at one time. The use of only some of the needed algaecide will not kill some of the algae. It is important to follow the directions for use on the package.

Age of the algae

The older algae becomes, the more difficult it is to control. Treat the problem as soon as it is noticed.

Sunlight and water temperature

It is best to treat when algae are actively growing. Sunny days and a water temperature of 60°F or higher will be helpful.

Type of algae

Different types of algae require different types of treatment.

Green Algae

The most common algae associated with swimming pools is green algae. It is very opportunistic, meaning it will take advantage of any failure in the normal sanitizing program and quickly infest a pool. One will see green algae problems frequently appear overnight following heavy rainstorms. This is because rainstorms actually provide food for the algae in the form of nitrogen. The nitrogen not only feeds the algae but also destroys chlorine residuals. Green algae must not be mistaken for metal present in the pool water.  Metals, especially copper, can give the water a clear green tint.  The best way to treat green algae is to prevent it in the first place. Use an algaecide regularly as part of a normal maintenance program. This will prevent algae from growing, even if a failure in the sanitizing system was to occur. It is always easier and more effective to prevent the algae problem than to try and eliminate it once it occurs. When it does occur, treat it promptly. The longer you wait before treatment, the more difficult and costly the result. Select an algaecide that will both kill the existing algae and prevent renewed growth. Follow the label directions and maintain circulation during treatment.

Yellow or Mustard Algae

Yellow or mustard algae is very similar in form to green algae, but is much slower growing and is deficient in chlorophyll (green pigment) which accounts for its yellow color.  It is easily identified by the ability to brush it easily off the pool walls and floor.   Because yellow algae grow very slowly, it is also very difficult to destroy. By the time you see it growing in your pool, it has likely been there as long as several weeks. Additionally, since yellow algae is low in chlorophyll which is light-loving, the algae live and even grow in dark areas of the pool such as plumbing and filters. This only compounds the difficulty of control. To treat mustard algae, care in selection of a proper algaecide is most important. Be certain to select a product made for the control of this unique form of algae. Copper-based algaecides seem particularly well suited for controlling yellow algae.  One word of caution: it is not unusual to need to treat yellow algae more than once to bring it fully under control. This again points out the value of preventing the growth in the first place.

Black Algae

Frequently considered the most difficult algae to control is the one we commonly refer to as "black algae". However, it is also likely the easiest to prevent. Black algae typically gain a foothold in areas of the pool that suffer from poor circulation. Areas such as corners, or in certain areas of the deep end, are often identified as places where black algae continue to show up in a particular pool and are then nearly impossible to eliminate. Most often, these areas suffer from inadequate circulation and thus little or no fresh water, sanitizer or algaecide gets to the area with any regularity. One of the best ways to prevent black algae growth or eliminate it once it surfaces, is to correct the circulation problem(s) first. Once it begins forming, black algae develops specialized cells that lock it deep in the pores of pool surfaces. In order to effectively control it, all of its cells, including those deep in the surface, must be killed. It is all but impossible for chlorine alone to get this deep into the pores of the pool. In addition to the attaching or locking mechanism of black algae, the growing colony also produces a defense mechanism. Outer layers of the colony produce a waxy coat that prevents chlorine or algaecides from penetrating into the colony and killing it. Therefore, the algaecide used should contain a "penetrating" agent. This agent will actually work to help the algaecide penetrate into the pores of the pool surface and cut through the waxy coat with a special wetting action that chlorine does not have.

The following steps will help in bringing black algae under control:

  • Correct any problems with the circulation pattern in the pool.
  • Brush the colonies as this will break through the waxy coating protecting the colony. This is an important step!
  • Add an algaecide intended for use on black algae.
  • Brush the colony daily thereafter, if possible, as this will remove any dead cells from the surface exposing the living cells underneath for exposure to the algaecide.

Following these simple procedures when treating Black Algae will not only help insure its successful removal, but reduce the likelihood of its return as well.

  • Any time algae develops in your swimming pool, it is best to consult your professional pool retail provider for the best solution available.
Chloramine Problems
Chloramine Problems

Because chlorine likes to combine with other elements in the water, it is effective at killing bacteria when they combine. However, when ammonia is present in the water, the two combine to form chloramines. When combined, the chlorine is in a weakened state and is not as effective against algae and bacteria.

Ammonia (Nitrogen) in the water can come from human sweat, urine, leaves and fertilizer. Because one active swimmer in the water can produce one quart of sweat in an hour, it is highly likely that ammonia will be present. When you smell chlorine in a pool or have irritated eyes, chloramines are the cause – not the presence of too much chlorine.  Chlorine gets a bad rap in this case.  Chlorine is by far the most efficient and effective way to control algae and bacteria in your pool. The only way to reduce the chloramines is to add more chlorine, shock, to neutralize the chloramines so that the chlorine will go back to oxidizing the bacteria and algae instead of combining with the ammonia in the water.

You can calculate combined chlorine in your water by subtracting the amount of free chlorine from total chlorine. This value should be as close to zero as possible.   Whether your pool is used heavily or not, chloramines can form in your pool.  Shocking on a weekly or biweekly basis is required.

Cloudy Water
Cloudy Water

You need to be sure that your pool water has adequate circulation, filtration and chemical treatment so that it remains clean and clear. There are a number of causes for cloudy water.   This would include:

  • Low chlorine
  • pH and/or alkalinity too high
  • High calcium hardness
  • Pool circulation and filtration.
  • Water Temperature.  As the water heats up during the spring and summer, it is more susceptible to clouding.

In order to maintain adequate circulation, you should run your pool pump at least 12 hours during the summer and 6-8 hours during the winter (pool pumps are designed to run 24 hours.  This will most assuredly help prevent cloudy water). Be sure to test your water regularly and add necessary chemicals to ensure proper balance. If you pool needs to be shocked, shock it and run the filter for at least 24 hours to see if that clears it up.

If your pool water still remains cloudy, contact a pool professional to test and clarify your water. Be sure the pool professional checks your equipment to be sure it is working properly. You should also be sure your filter is cleaned at least twice a year.

Total Dissolved Solids
Total Dissolved Solids

Total dissolved solids (TDS) is the sum of all materials dissolved in the water and normally runs in the range of 250 ppm and higher.

There is much discussion over what levels are considered too high, but there is no real lower limit. TDS is comprised of many different chemical compounds, which means that the issue of how much is too much actually depends more on what they consist of than how much there is. In general, when the TDS exceeds approximately 1500 ppm, problems may begin to occur.

It must be pointed out that pools whose sanitizing systems are based on chlorine or bromine generation equipment will likely have much higher TDS levels. These pools actually have salt in one form or another added to the pool. The salt used is highly soluble and does not cause the type of problems normally associated with high TDS, but it does add to the TDS level in the pool, as will any chemical. When testing water in this type of pool for TDS, the salt intentionally added to the pool needs be taken into account.

At elevated levels, TDS can lead to cloudy or hazy water, difficulty in maintaining water balance, reduction in sanitizer activity and foaming. Unfortunately, the only way to reduce TDS is to drain a portion of the water and replace it with fresh water. Sequestering agents do not help when high TDS levels are causing cloudy water.

pH and Pool Water
PH And Pool Water

pH is the term used to refer to the degree of activity of an acid or base (alkali) in the water.  It is the most important chemical factor to be maintained in swimming pools. pH is measured on a scale from O to 14 with 7 being neutral. Pool water pH is best when kept in the range of 7.2 to 7.8.

A value of 7 to 14 is considered basic with 14 being the greatest base activity.  Another word for basic is alkaline; however, this is not to be confused with total alkalinity. pH and total alkalinity are not the same but can be influenced by each other.

A pH value between 0 and 7 is considered acidic with 0 being the greatest acid activity and getting weaker as it approaches a value of 7. When pH remains below 7.2, the water is considered to be corrosive. This means etching of plaster and metals in equipment such as heat exchangers will result. In addition, it is more difficult to keep chlorine in the pool because while more effective as a sanitizer at the low pH, chlorine is also much less stable resulting in the consumption of larger quantities of chlorine than would be used at normal pH levels.

Maintaining the pH higher than 7.8 will increase the tendency to form scale or cloudy water. Calcium, the major component in scale, is a relatively unstable mineral and when the pH is high, the calcium is not as soluble and it will have a greater tendency to precipitate or "fall out" of solution resulting in cloudiness or scale. High pH will also reduce chlorine effectiveness resulting in the need to maintain higher chlorine levels to achieve maximum sanitization. If the pH is low, a pH increaser is added to raise the pH. If the pH is high, pH Down is used. pH Down comes in two forms: liquid acid or dry acid.

Changes in the pH of pool water can be caused by many factors but one of the most significant cause is the sanitizer used. Since the sanitizer is the most frequently added chemical in pools, it can have a powerful impact on pH and overall water quality.

Of the sanitizers typically used in pools, chlorine is the most common. Chlorine comes in a variety of forms and varies widely in pH. For example, most tableted forms of chlorine have a very low pH and will tend to lower pH over time, while liquid chlorine is very high in pH and will tend to raise pH values.  Salt is also very alkaline and will require frequent additions of acid to maintain the proper pH and overall water balance.

Changes in pH due to sanitizers or other factors can be minimized and controlled by the proper maintenance of the next chemical factor, total alkalinity.

What is pH?

Metal Problmes
Metal Problems

When metals are present in pool water, they will need to be removed as soon as possible so that they don’t stain your pool. You should regularly add a metal sequestering product (stain and scale preventer) before you have any issues. If you are unsure of what to add, be sure to have your pool tested for metals by a pool professional at least once a month. If you test your pool water and see that the water shows a metal level of .2ppm or above, it is advisable that you add a stain/scale preventer weekly or bi-weekly. A good rule of thumb is to alternate your weekly shocking with weekly stain/scale preventer.

A metal sequestering product will grab the metal where it will be filtered out by your pool’s filter – keeping it from staining your pool walls. You should run the filter continuously for 24 hours after adding it to remove as much as possible. This will also prevent scale formation on pool surfaces and equipment.

Staining and scaling of pools is most noticeable in white plaster pools but it is best to identify the source and type of staining to know how to treat it. A copper metal stain will appear aqua or blue while iron stains will appear a rust or black color. The presence of manganese will appear black. Scale will appear as splotchy gray or brown and is rough to the touch.

The metals present in water are caused by the metals in your water supply, from erosion and corrosion of metal fixtures/fittings and even fertilizer.  If stains appear, be sure to adjust the pH and alkalinity to recommended ranges. You should then vigorously brush the stained areas. Add the metal out treatment and run the filter. Two days later, you should shock your water. You should then retest your pH and alkalinity. If your metals are still present repeat the process.

Identifying and treating metal stains can be challenging. It is recommended that you consult your pool professional prior to any treatment process.

Calcium Hardness
Calcium Hardness

The sum of all the calcium dissolved in water is referred to as the calcium hardness.    Calcium is important since high levels are unstable and become even more unstable if the pH or the total alkalinity rise above the normal levels. These imbalances can result in cloudy water and/or scale. In addition, calcium does not like warm water. As water temperature rises, calcium becomes more likely to precipitate out of solution. Calcium is actually more soluble in cold water, which is why scaling of heater equipment is so common.

With all of the difficulties calcium can cause, it would seem logical to use soft water in filling a pool. However, this is not the case! While high calcium levels can cause problems with cloudy water and scale, soft or low-calcium water is also of concern. Such water is aggressive and will actually remove calcium from plaster in order to satisfy its need for the mineral. If the pool is vinyl or fiberglass, the low calcium water will actually attack metal fittings and heat exchangers resulting in destruction of the fittings or pinhole leaks in the heater. When such corrosion occurs, it is also common for stains to appear on pool surfaces.  It will also damage the vinyl or fiberglass surface you may have.

Calcium content is best in the range of 100-400 ppm and is water temperature dependent. Unlike pH or total alkalinity, however, both of which can be raised or lowered with reasonable ease, calcium levels cannot.

Adding a hardness increaser to the water easily raises calcium levels. Conversely, there is no simple chemical addition that can be made that will reduce calcium hardness. The only way to reduce calcium hardness levels in pool water is through dilution with water of a lesser hardness. Over time, calcium hardness will naturally increase in pool water due to evaporation and possibly other factors unless the pool water is regularly diluted.

While it may be difficult to reduce calcium hardness, it is possible to control it so that a potential problem such as cloudy water or scale formation is prevented. The best way to minimize the effect of high calcium levels is through the use of a sequestering agent. A sequestering agent is a compound that, when added to water, will chemically bond with calcium and other minerals to make them, in a sense, more soluble. This means that calcium will still be present, but in a form that is less likely to cloud water or form scale if the pH or other factors get out of balance. In addition, since calcium will still be in the water, you will not have the corrosion problems you would otherwise experience with soft water. A further advantage is that elevated levels of calcium (over 400 ppm) can be tolerated without constant need for dilution. This becomes especially important when the pool is located in hard water areas or calcium-based chlorine sources are used.  A sequestering agent should be a part of your regular chemical maintenance program.

When dealing with calcium harness issues in your pool, it is suggested that your first line of defense is your local pool professional.  They can prescribe what is best for your pool to take care of and prevent any problem that can arise.