Pool Water Chemistry

Maintaining proper water chemistry is essential to the enjoyment of your pool and the safety of your swimmers! Some of the chemicals you’ll use include: Disinfectants to destroy harmful or unwanted organisms; Alkalinity and pH Adjusters to maintain a consistent acid-base relationship; Chlorine Stabilizer to prevent unnecessary loss of chlorine; Algaecide to kill and prevent algae, and Filter Aids to help remove foreign material.

pH

pH is the single most important element in swimming pool water chemistry. It affects every other chemical balance in pool water.

pH indicates the relative acidity or basicity of pool water. pH is measured on a scale of 0 (strong acid) to 14 (strong base) with 7 being the neutral pH.

In pools, a slightly alkaline pH of 7.4 to 7.6 is most desirable because this range is most comfortable to the human eye and provides for optimum use of free chlorine while maintaining water that is not corrosive or scale forming.

If pH is too low (below 7)

• Water becomes acidic
• Chlorine residuals dissipate rapidly
• Eye irritation occurs
• Plaster walls are etched
• Metal fittings, pump impeller, heater core may corrode
• Dissolved metals may leave stains on walls
• Rapid Loss of alkalinity

If pH is too high (above 8)

• Chlorine activity is slowed and inefficient
• Scale formation and discoloration of pool walls
• Water becomes cloudy
• Filter is overworked
• Eye irritation may occur

If you need to adjust your pH level, please refer to the instructions on the packaging or to the amount indicated on the results of your computerized water testing. Be sure the pump is running when chemicals are added. Allow water to recirculate then retest to determine if further treatment is necessary. If problems with low pH persist, it may be necessary to raise total alkalinity to stabilize the pH.

Total Alkalinity (TA)

Total alkalinity is closely associated with pH. Total alkalinity is a measure of water's resistance to change in pH.

Total alkalinity should be maintained in the range of 80 to 150 ppm.

If total alkalinity is too low:

· pH changes rapidly when chemicals or impurities enter the water. pH may drop rapidly, causing etching and corrosion.

If total alkalinity is too high:

· pH becomes difficult to adjust. High pH often occurs causing other problems such as; cloudy water, decreased disinfectant effectiveness, scale formation and filter problems.

Calcium Hardness

Calcium hardness is a measure of the dissolved calcium salts in water. Under normal conditions this should not be a problem in properly operated swimming pools. If calcium hardness is very low then water may leach calcium from pool walls causing pitting of the plaster surface. Very high calcium hardness may contribute to scale formation and clouding of the water. To raise calcium hardness - add calcium chloride.

Total Dissolved Solids (TDS)

After a pool has been in use for a time, dissolved solids may begin to accumulate. These unfilterable solids include body wastes, suntan lotion, stabilizer, chlorines, algaecide, dirt, pollen, etc. Normally this is less of a problem with outdoor pools because of rain water and no use during winter months. Ideally pool water contains under 450 ppm total dissolved solids.

Conditioner/Stabilizer

Stabilizer or Conditioner is used to decrease the suns effect on chlorine. If your pool is indoors or if you don't use chlorine as a sanitizer, then you don't need it. The suns ultra-violet rays break down and neutralize free chlorine so that it has no sanitizing qualities. Stabilized chlorine compounds such as DiChlor and TriChlor contain stabilizer and release a small amount each time you add chlorine to the water. Other chlorine compounds such as chlorine gas, sodium hypochlorite, calcium hypochlorite and lithium hypochlorite contain no stabilizer and are referred to as unstabilized chlorine compounds.

The use of Stabilized chlorine products such as DiChlor and TriChlor are a simple way to insure levels of both Chlorine and Stabilizer are kept within the recommended levels.

Stabilizer is toxic and actually diminishes the effects of chlorine by slowing down its reaction with wastes. Therefore, there is no reason to keep the levels above 100 PPM.

Disinfection of Pool Water

A proper balance of the water chemistry factors described above will provide water that will not damage pool components and is non-irritating to swimmers. Now, it is necessary to disinfect the water to prevent the spread of disease organisms from person to person and prevent unwanted growth of bacteria and algae in the pool.

The most commonly used disinfectant for swimming pools is chlorine.

Free Chlorine Residual is the amount of chlorine in the pool which has not reacted with substances other than water. It is the chlorine which is available to disinfect pool water and oxidize organic substances. Free chlorine residual should be maintained between 1 and 3 ppm.

Combined Chlorine is chlorine in the pool which has reacted with substance other than water and is no longer available in its free state. Some combined chlorines are bactericides but they contribute little to the disinfection process. Chlorine combined with ammonia produces chloramines which cause eye irritation and an objectionable chlorine odor. For this reason combined chlorine residual should be kept to a minimum preferably below 0.2 ppm. 

Total Chlorine residual is the concentration of free chlorine plus combined chlorine. To determine combined chlorine residual test for free chlorine and total chlorine.

Total chlorine - free chlorine = combined chlorine