Pool Water ChemistryPool Water Chemistry



  Home  |  Pool Encyclopedia   |   Pool Water Chemistry


Above Ground Pools

Pool Supplies

Pool World Encyclopedia

Email Us



Pool Water Chemistry

Pool water chemistry is the most misunderstood, yet vital component to overall pool care. Not only does proper water chemistry protect the swimmers using the pool, but it also protects the swimming pool itself. Gas heaters, electrical heat-pumps, filters, and even the vinyl-liner can all suffer severe damage from unbalanced pool water. In order to clear up some of the confusion surrounding this subject, we have listed some of the more important water chemistry terms below.

The Chemistry of your pool water is sometimes the most confusing, yet most important part of your pool care.  Proper pool Chemistry will protect the swimmers, the pool and your pool equipment. Any piece of pool equipment that is touched by pool water can be damaged if the water chemistry is not properly balanced.  So lets look at some of the issues regarding pool water chemistry.

Calcium Hardness
Calcium Hardness speaks to how much Calcium ( or other hardeners like magnesium) is in your pool. Too much Calcium hardness can result can cause scale, which  can make the water cloudy and form residue on pool ladders and equipment. Calcium Hardness that is too low can lead to corrosion of metal products in contact with your pool water.  The Correct levels for Calcium  Hardness should be between 150 and 300 parts per million.

Chlorine Sanitizers

Chlorine Sanitizers fulfill two functions. First, they sanitize your pool water, that is killing all the the bacteria that can accumulate. Secondly, they oxidize your pool water breaking down  ammonia, and other swimmer related by products. They also, in proper levels kill algae spores before they have a chance to propagate. Levels of sanitizers must be kept at optimum levels so they can quickly kill or treat whatever contaminates that can come into your pool waters. The Amount of active chlorine in your pool water should be in the range of 1.5 and 3.0 parts per million.


TA  (or total alkalinity)

TA refers to how much alkaline products there are in your pool water. Alkaline products protect your pool water from abrupt fluctuations in pH. TA that is too low can lead to corrosion of metal parts and can damage the vinyl liners of Above ground pools. You should test often to determine proper Alkalinity levels,    which should be 110 parts per million for pools that use stabilized chlorine and 80 parts per million for granular styles of Chlorine.


Acidity/Alkalinity  (pH)

the symbol for the logarithm of the reciprocal of hydrogen ion concentration in gram atoms per liter, used to express the acidity or alkalinity of a solution on a scale of 0 to 14. I t expresses the acidity or alkalinity of water.  A pH reading of 7 is considered neutral  lower than 7 and the water becomes acidic, higher and it becomes alkaline. A pH level of 7.2  to 7.8 is considered idea.


Stabilizer, usually Cyanuric acid , is used to prolong the potency of Chlorine in the water of a swimming pool. Of the two types of chlorines that are available on the market there are stabilized and non stabilized. Granular chlorine, tend to be more potent than it's Stabilized cousin and more effecting at treating algae or cloudy water.  If you use non-stabilized chlorine you should add stabilizer to your pool each spring after balancing the pool water. Cyanuric Acid levels  are optimum in the 40 to 80 parts per million range


Possible Problems derived from off balance pool chemistry.

Cloudy or unclear water
Pool water can turn cloudy for a variety of reasons. The most common cause of cloudy water is either dead algae floating in the pool water or other small particles floating in the water such as dissolved leaves. The best way to treat a cloudy pool is chlorine, chlorine, and more chlorine. You should add a large dose of non-stabilized chlorine (either calcium hypochlorite or sodium hypochlorite) each day for four to five days straight, keeping your free chlorine level above 3 ppm at all times and running the pool filter 24 hours a day. If this does not clear your water, then you can try clarifiers and other products. But first shock your pool water.

Algae are microscopic plants which can transform your pool water from clear blue to a swamp in as little as 24 hours. Algae spores are introduced into the pool through the air, from rain water, and from swimmers walking across the grass and then jumping into the pool. Algae blooms are common after heavy rain showers and when the pool water temperature is high. There are many types of algae, the most common in our area being green algae, mustard algae, and black algae. The most effective way of preventing algae growth is to maintain a free chlorine level of at least 1.5 ppm at all times, run the pool filter 24 hours a day, and to add a dose of algaecide once a week. We have also found that adding Sun Algaecide to the pool water decreases your chances of suffering from an algae bloom. a Sun Algaecide acts as an inhibitor against algae growth by lowering algae's ability to process carbon dioxide in the water making it difficult for an algae spore to germinate and grow. If you do develop algae, apply the appropriate algaecide, shock the pool, and brush down the entire pool causing the algae to become suspended in the pool water. The next day, if anything settles out, vac it out to "Waste".

Tinted Water and Stains
If minerals are present in the pool water, they can cause the pool water to turn green, brown, yellow, and even purple. The water would look clear but discolored. It can be very difficult to distinguish between green water caused by green algae and green water caused by a mineral problem. A telltale sign of a mineral problem is the discoloring of the pool water shortly after shocking the pool. If this occurs, you will need to add a mineral sequester to the pool. Exactly how much is a guess. We have seen cases where one bottle has solved the problem, and others where multiple bottles were needed. Mineral problems are a tough nut to crack and the pool industry is just now trying to get a handle on it. Stains on the vinyl liner are also treated by adding a mineral sequester. Persistent stains might need to be treated with an "on contact" product that must be applied directly to the stained area of the pool. If the stain is on the bottom of the pool, applying the product directly on the stain can be tricky, but possible.

Low pH
Due to the acidic nature of our tap water and our rain, we tend to suffer more from low pH pool water than from high pH pool water. Fortunately, correcting the pH balance of your pool water is quite simple. All you need to do is add pH Increaser (also called soda ash and base). But before you add pH Increaser be sure to get your Total Alkalinity balanced first. Once the Total Alkalinity is balanced, the pH can be adjusted more accurately.