LaMotte Pool Manager Water Quality Handbook - Manual (Page 17)

Alkalinity
What is Total Alkalinity?
Total alkalinity is a measure of the acid-neutralizing
capacity of the water supply which enables it to resist
abrupt changes in pH. Total alkalinity is commonly
known as a pH stabilizer because, at proper levels, a
consistent pH level can be maintained while treatment
chemicals or fresh make-up water is added.
Commercially available chlorine treatment compounds
can range in pH from 3.0 to 13.0, and make-up water
can range in pH from 5.0 to 8.0. Therefore maintaining
total alkalinity at recommended ranges is extremely
important.
Why do we test Alkalinity?
The purpose of testing alkalinity is to determine how
susceptible the pool water is to rapid pH changes. A low
level of total alkalinity allows the pH to fluctuate or
“bounce” when materials are added, even in small
amounts. A high level of total alkalinity can have the
reverse effect, limiting the ability to change pH levels
which may be too high. Total alkalinity is a measure of
acid-neutralizing materials in the water, therefore it is
normal to see high
alkalinity when the
pH is also too high.
A moderate or
ideal alkalinity
allows the pH to be
maintained
without requiring
constant chemical
adjustments.
Alkalinity tests
should be
conducted once a
week.
15
Ideal Alkalinity
Low Alkalinity
Allows to bounce pH
Allows proper pH control
High Alkalinity
Usually means high pH
and is hard to adjust
pH reading
pH reading
pH reading