The most important element in swimming pool care is the pH. The pH level affects all other chemicals in the water. The pH is measured on a scale from 0.0 to 14, with 0.0 being strong acid, 14.0 being strong base and 7.0 being neutral. The acceptable pH for a swimming pool is between 7.2 and 7.8.
Although a pH reading of 7.2 to 7.8 is acceptable for a swimming pool, the ideal range is 7.4 to 7.6. If the pH is lower than 7.2 or higher than 7.8, the other pool chemicals are affected and will not work the way the chemicals are intended. Unacceptable pH readings in the pool can cause other issues with the water.
When the pH is lower than 7.0, the water can become acidic and chlorine will rapidly dissipate. Swimmers can experience eye irritation and metal fittings in the pool, pump and heat can corrode if the pH is not raised right away. When metals start corroding, stains can appear on the pool walls. Low pH in the pool will reduce the total alkalinity in the water and well. Rain water is a natural occurrence that will lower the pH in the pool as well as organic waste or litter.
Pool water with a pH reading higher than 8.0 can cause eye irritation in swimmers and cloudy pool water. The chlorine becomes inefficient and slows down, scale formations can appear on fixtures and pool walls and the filter is overworked and can short cycle (turn off and on during filtration). Natural occurrences such as the presence of algae or swimmer's waste in the pool can raise the pH level.
Raising and lowering the pH in the water requires chemicals especially for the job. Raising pH is done using soda ash and muriatic acid is used to lower the pH. Soda ash is used at two-thirds oz. per every 1,000 gallons of water to raise the pH 0.2 parts per million to reach the ideal pH reading. Muriatic acid is added at 11/4 oz. per every 1,000 gallons of water to lower the pH 0.2 parts per million to achieve the ideal pH reading.