LaMotte Pool Manager Water Quality Handbook - Manual (Page 14)

The pool water pH should be tested several times a day
in a public pool with moderate-to-heavy swimmer usage.
The pool’s pH level is constantly being changed by
chlorine or other treatment chemical additions.
Swimmer usage, additions of fresh make-up water,
leaves, and debris can also alter the pH slightly.
The obvious reason to test pH is not only to identify a
problem but to accurately decide how to remedy the
problem. If a water test reveals a highly basic pH, such as
8.2, then the water supply needs to have an acidic
substance added to bring the water back down to a pH
of about 7.4. This need is called an “acid demand” and
can be corrected by adding a liquid acid (muriatic acid)
or a dry acid (sodium bisulfate).
If a water test shows an acidic pH level, such as 6.8, then
a basic substance should be added to bring the water
back up to a pH of about 7.6. This need is called a “base
demand” and can be corrected by adding soda ash
(sodium carbonate) to the water.
High pH
®
Acid Demand
Low pH
®
Base Demand
See pages 44-45 for pH treatment charts.
12
pH
LOW
If pH is too low (Acidic)
•
•
•
•
corrosion of pool equipment/staining
swimming eye irritation
etching plaster pool surfaces
chlorine dissipates quickly
pH
HIGH
If pH is too high (Basic)
•
•
•
•
scale accumulates on pool equipment
cloudy, turbid water
chlorine sanitizing power is weakened
swimmer eye irritation