LaMotte Pool Manager Water Quality Handbook - Manual (Page 20)

Inadequate levels of calcium
hardness also need to be avoided. In
plaster pools, aggressive low
hardness water can result in etching
or pitting in the plaster. Pools with
inadequate hardness levels are
susceptible to corrosion of metal
parts in the pool or heat exchange
systems.
Fortunately water does have a saturation point where it
is no longer aggressive and will not deposit scale on pool
surfaces, providing maximum protection to the pool
surface and its parts. This condition is called “water
balance,” and can only be obtained when the pH, total
alkalinity, calcium hardness, and temperature factors are
all at recommended levels.
How do we test Calcium Hardness?
To test calcium hardness a titration procedure is utilized.
An indicator is added to the test sample to produce a
color indicating the presence of calcium. The sample is
titrated with another reagent until a color change occurs
and the titration is complete. Next, the result is
calculated from the volume of titrant used or is read
from a calibrated dispenser or test vial. Always read the
test instruction carefully to determine the proper color
change and procedure, watching closely for the
complete color change from the original color.
Ideal Ranges for Calcium Hardness
Spas: 175 - 300 ppm
Pools: 200 - 400 ppm
18
Scale can clog pipes