Water Chemistry For Swimming Pools

Proper water chemistry is essential to maintaining safe and consistent swimming pool operation.  Chemicals
used in swimming pools include: Disinfectants to destroy harmful or otherwise objectionable organisms; 
Alkalinity and pH Adjusters to maintain a consistent acid-base relationship and acid buffering capacity; Chlorine
Stabilizer to prevent unnecessary loss of chlorine; Algicide to kill and prevent algae, and Filter Aids to help remove
foreign material.  Following is a discussion of various factors which affect water chemistry, how they affect
swimming pools and hot to use pool chemicals to restore a properly balanced water chemistry.

pH - Why you need to Balance It!!!!

pH Is the single most important element in swimming pool water chemistry.  It affects every other chemical
balance in pool water.

pH is a measure of hydrogen ion (H+) concentration in water.  It indicates the relative acidity or basicity
of pool water.  pH is measured on a scale of 0 (strong acid) to 14 (strong base) with 7 being
the neutral pH.

In pools a slightly alkaline pH of 7.4 to 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.

If pH is too low (below 7)

• Water becomes acidic

• Chlorine residuals dissipate rapidly

• Eye irritation occurs

• Plaster walls are etched

• Metal fittings, pump impeller, heater core may corrode

• Dissolved metals may leave stains on walls

• Rapids loss of alkalinity

If pH is too high( above 8)

• Chlorine activity is slowed and inefficient

• Scale formation and discoloration of pool walls

• Water becomes cloudy

• Filter is overworked

• Eye irritation may occur

pH adjustment

To avoid the problems listed above, pH must be maintained between 7.2 and 7.8.  The
most desirable level for pH is between 7.4 and 7.6  If pH is too low - run alkali demand test
if available.  Raise pH by adding soda ash (sodium carbonate).  Never add more than 2 LBS
10,000 gallons in a single treatment.  Be sure the pump is running when chemicals are added.
Allow to recirculate 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.