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.
