Join our mailing list!

You are here: Home > WATER CHEMISTRY > pH


The pH of your water can be affected by a number of factors, including geography, temperature, and biological loading.

pH is the most important chemical that needs to be maintained in swimming pool or spa water chemistry due to its effects on  every other chemical to obtain a perfect  water balance. pH is a measure of hydrogen ion (H+) concentration in water and is the intensity of acid or alkaline elements in your pool or spa. It indicates the relative acidity or alkalinity in your pool water. 7.0 is the neutral pH level for water and is measured on a scale of 0 (extremely acid) to 14 (extremely alkaline).

Low pH is measured as less than 7.2 and is considered corrosive or acidic and can cause eye and skin irritation and corrode metal fixtures including metal components found ionizers, gas heaters and electrical heat-pumps. A High pH level above 7.8 is considered as basic, scaling, alkaline and can cause eye and skin irritation, reduce the sanitizing action of chlorine, and cause the water to appear cloudy.

In pools and spas, a slightly alkaline pH of 7.4 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. A pH level between 7.2  to 7.8 should always be maintained top insure the effectiveness of the sanitizer/ disinfectant.

You can raise pH with borax or soda ash/washing soda. Soda ash/washing soda will increase the total alkalinity more than borax will. You can lower pH with muriatic acid or dry acid. How much you will need for a given pH change depends on several other numbers, most importantly total alkalinity and borate. Higher total alkalinity and/or borate levels cause you to need larger amounts of chemicals to change the pH.

Note that the type of sanitizer you use (chlorine, bromine, biguanide, minerals, salt, etc.) can affect your pH, as can rain water and virtually everything else that enters your pool. It's therefore very important to test and adjust your pH on a regular basis.

If pH is too low (below 7.2)

Water becomes acidic

Chlorine residuals dissipate rapidly losing its ability to sanitize and disinfect

Eye and skin irritation occurs

Will damage vinyl liners and plaster walls will most likely become etched

Metal fittings and plumbing, pump impeller, heater core can corrode

Dissolved metals may leave stains on walls

Rapid Loss of alkalinity

More likely algae growth

To improve on a low pH level, take the following steps. Raise pH by adding soda ash (sodium carbonate). Never add more than 2 pounds per 10,000 gallons in a single treatment. Be sure the pump is running when chemicals are added so proper circulation and dissolving of soda ash occurs. Allow the pump to recirculate the water and then retest to determine if further treatment is necessary. Caustic soda (sodium hydroxide) is sometimes used with chemical feed pumps to raise pH. If problems with low pH persist, it may be necessary to raise total alkalinity to stabilize the pH.

If pH is too high (above 8)

Chlorine activity is slowed and ineffective losing its ability to sanitize and disinfect

Will damage vinyl liners and scale formation and discoloration of pool walls, plumbing or equipment

Water becomes cloudy, hazy or dull

Filter is overworked

Eye and skin irritation may occur

If your pH level is too high, lower it by adding pH Reducer. Add carefully, following all label instructions. You should adjust the level gradually, adding no more than 1 lb. per 10,000 gallons of water (per treatment). Make adjustments in doses, re-test the water after 2 hours before repeating the application. And do not add more than 2 1/2 lb. per day.