Pool and Spa pH
pH indicates if a solution is acidic or basic. It is measured on a scale of 0 to 14. Pure distilled water has a pH of 7.0 which is neutral. Solutions below 7.0 are considered acidic and those above 7.0 are basic. Swimming water should be kept above 7.0 and never above 7.8. 7.2 to 7.6 is the ideal range. Ideally pH should be checked daily on spas and heavily used pools but in any case it needs to be checked no less than once a week.
Water and other substances in solution break up into positive and negative charged particles called ions. Water (H2O) becomes H+ and OH-. When these are in equal amounts as in pure distilled water the pH is 7.0 or neutral. When you add other substances to the water you become more acid if the substance adds more positive ions and basic if there are more negative ions. The pH does not tell how much acid or base is in the water, but only how much is ionized.
It is important to have accurate pH in swimming water because it effects everything else that is in the water from how well the sanitizer kills bacteria and how long the equipment survives to how the water feels to the bather.
A pH that is too high (above 7.8) causes the formation of scale, ineffectiveness of chlorine and irritation too bathers, A pH that is too low (below 7.0) causes corrosion the loss of chlorine and irritation to bathers.
pH can be raised by the addition of soda ash or sodium bicarbonate and other more complicated substances sold by some pool stores. pH can be lowered with acids such as Muriatic Acid (HCl or hydrochloric acid) or acid salts such as dry acid (sodium bisulfide).
It is importance that you thoroughly read and understand all the directions and cautions that come with any chemicals that you use. Misuse can lead to serious injury. Never adjust the chemicals in a pool or spa while it is being used. All bathers must exit the water while it is adjusted and remain out of the water for the recommended period of time in the instructions.
Under no circumstances should you add water to the chemicals if the instructions call for a dilution to be made. Always add chemicals to water.
When you get your chemicals for adjusting your pool and spa they will tell you how much to add to get the correct pH. Always add large amounts of chemical required in small doses over a period of time. Allow the chemical to circulate through the water and retest before the final addition to minimize over shooting your goal. This may seem like a waste of time but in the long run it will save your time from having to readjust. In the business of adjusting a pool slow and careful pays off.
You will need to lower the pH usually more often than raise it. Most things that go into the water will raise the pH. This includes the sanitizer we add, the wastes (sweat, urine, etc.) from human use and things that wash in from nature (dirt, leaves, etc.). Water in puddles that have been standing for a while will have a pH in the low 8’s.
Once the pH is adjusted you will be ready to go on to sanitation.
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