pH is how acidic or alkaline the water in the hot tub is
In a spa, pH is very important. Low pH can damage surfaces and equipment and can cause eye and skin irritation, while high pH can cause scale buildup and cloudy water. Proper pH balance is also necessary for the sanitizer to work the most efficiently. But, it is often difficult to maintain pH in the ideal 7.4 - 7.6 range.
Test the pH twice a week and adjust as needed.
High pH
There are several factors that tend to increase pH in spas.
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Aeration: The bubbles introduced into the spa by the blower impacts the water balance. The buffering for spas is based on a carbonate system. Carbon dioxide, the carbonate ion, the bicarbonate ion and carbonic acid work together to buffer the water against excessive swings in pH. However, the aeration causes the carbon dioxide to leave the water. The result is an increase in the hydroxide ions, which causes the pH to increase.
- Circulation: Spas have a much faster turn-over rate than pools. The water moves more rapidly through the piping, which has more turns than the piping in a pool. As water flows through the elbows of the piping, the more rapidly moving water creates a difference in the pressure on the water that causes carbon dioxide to exit the water. Once again, the effect is an increase in pH and a decrease in total alkalinity.
- Water temperature: Higher operating temperatures for spas impact the pH similarly to aeration. The tendency for carbon dioxide to leave the water is increased as the temperature of the water increases, which in turn lowers the pH.
Low pH
Low pH is usually attributable to low Total Alkalinity and/or use of Brominating tablets. (Note: SpaGuard® does not recommend the use of trichloro chlorinating tablets in spas because of the potential for surface damage.) Brominating tablets can cause the pH and the total alkalinity to drift down rapidly. If these products are being used, check pH frequently to avoid equipment damage.