The most common form of chlorine for swimming pool consumption is calcium hypochlorite containing 70% available chlorine. This solid, white material is available in either a powder, or tablet form. Both have excellent stability under all normal storage conditions. In use, this material dissolves quickly, and releases free available chlorine which is needed to kill bacteria.

There are a number of factors which affect the rate at which chlorine is consumed in the swimming pool. Chlorine dissipates more rapidly in warm water than in cold water. The presence of organic matter such as perspiration and bacteria carried in bather’s skin all affect the rate at which chlorine is consumed as well as affects the amount of chlorine needed to maintain an adequate chlorine residual. For these reasons, it will be necessary to add more chlorine on sunny hot days and when there are more people using the pool.

Calcium hypochlorite should be added to the water by means of a chemical feeder or a dispensing basket. If tablets are used, remember that it may bleach a spot on the floor of the pool if permitted to rest there. Extreme caution should be taken to make sure that they are beyond the reach of children. Don't ever mix chlorine with any other chemicals !!! Always use a clean dry measuring device when handling this material since any contamination may result in a chemical reaction which may cause a fire.

Chlorine should be added to the pool approximately 15 minutes prior to swimming. Tests for the presence of a chlorine residual. Adjustments should be made frequently and additions of chlorine made as needed.

In your pool it will manifest itself in the form of slime on the sides and floor of the pool, and a general cloudiness in the body of the water accompanied by a sudden increase in the pH. In an advanced stage of growth, it will take on a green color and if allowed to progress further, a brownish color with an obnoxious fish type odor. Intense sunlight is very conducive to algae growth due to higher than normal water temperatures and an increased rapid loss of residual chlorine.

As a rule of thumb, algae growth will not develop where a proper chlorine residual is maintained. However, it is most difficult to maintain a proper chlorine residual in situations when intense sunlight and higher water temperatures increase the consumption of chlorine. Therefore, making it more expensive to control the growth of algae. When algae build up gains an advantage on your pool, a "shock" treatment(s) is often necessary to remove the growth. This consists of applying from five to ten times the normal amount of chlorine, when the pool is not in use. Allow the chlorine residual to settle back to normal before resumption of swimming.

Another factor in favor of algaecides, is that they require much higher concentrations of available chlorine than do bacteria in order to kill them. There are many types of algaecides, the most popular of which are the quaternary ammonium compounds and copper based products. Most quaternary ammonium compounds are in liquid form. Since they tend to decompose rapidly, frequent additions are required in order to maintain the proper active residual. On the other hand, copper based products are predominantly in a granular form and require only a single application of a proper dosage with occasional additions to compensate for dilution due to addition of new water.

While chlorine may be considered an effective algaecide, in order for it to be effective, its presence must be felt. Conditions under which algae grows most rapidly is precisely the same when it is most difficult to maintain an adequate chlorine residual. Therefore, it has become common practice to employ algaecides to control the growth of algae leaving the chlorine free to act on bacteria.

PH is a measure of acidity or alkalinity. To help us express numerically how acidic or alkaline, we use the pH scale.

The PH scale runs from 0 to 14. A PH reading between 0 and 7 is on the acidic side. A PH of 7 is neutral, and pH readings between 7 and 14 is alkaline. The PH of swimming pool water should be controlled within the range of 7.2 to 7.8.

Water that is decidedly acidic or alkaline is uncomfortable to swim in. Irritation to eyes, skin, and bleaching of hair and swim suits is usually caused by improper PH. Human beings feel comfortable in a relatively narrow PH zone (7.2 to 7.8) and the effectiveness of chlorine is greatest in this same range.

Pool water which is acidic, (PH below 7) is corrosive to filters, pipes, and other metal fixtures. It will result in excessive chlorine consumption. An overly alkaline water (PH above7) tends to form unsightly white-ish deposits called "scale," which adhere to pool fixtures. In this alkaline range, the effectiveness of chlorine is greatly reduced.

Swimming pool water is considered hard when it contains dissolved solids. Calcium, magnesium, iron, and manganese are the chemicals of primary concern. These minerals enter the pool in the water supply, and/or may be picked up from piping and pool accessories used in the pool system. The presence of calcium and magnesium contribute to white cloudy water,while iron and manganese usually cause discolored water.

Most hard water conditions can be alleviated through the addition of water softening agents. Cloudy water conditions caused by calcium and magnesium are usually the result of too high a PH and may be easily corrected by adjusting the PH to between 7.2 and 7.8.

Well water or ground water usually contain high percentages of iron and manganese. Pool waters which contain these minerals may not initially appear to have any color, but upon adding chlorine, they may be oxidized and will appear as a yellow to brownish color. Colored water may be eliminated by the addition of water softening agents.