We use pH as an index to express how acidic or basic a solution is. (The scientific definition of pH is “the negative logarithm of the hydrogen ion concentration”.) A pH greater than 7.0 is basic, and a pH lower than 7.0 is acidic. In pools and spas, it is important to maintain the water in the slightly basic range of 7.2 to 7.8. The National Spa and Pool Institute (NSPI), the industry association in the United States, has set a standard of 7.2 to 7.6 as the ideal pH.

If pH Is Low:

If pH Is High:

Adjusting pH

You want the pH level between 7.2 and 7.8
The pH of a human eye is 7.5

Raise pH by .2:
ozs of sodium carbonate = gals x .0008

Lower pH by .2:
ozs of sodium bisulfate = gals x .001

To Lower pH by .2 in 9,500 gallons of water.
Use 9.5 oz's of Sodium Disulfate.

To raise pH by .2 in 9,500 gallons of water.
Use 7.5 of Sodium Carbonate.