Raypak 503-2003 - Manual (Page 18)

18
Pool/Spa Water Chemistry
Water Hardness
Water hardness is mainly due to the presence of cal-
cium and magnesium salts dissolved in the water. The
concentration of these salts is expressed in mg/L, ppm
or grains per gallon, as a measure of relative hardness
of water. Grains per gallon is the common reference
measurement used in the U.S. water heater industry.
Hardness expressed as mg/L or ppm may be divided
by 17.1 to convert to grains per gallon. Water may be
classified as very soft, slightly hard, moderately hard
or hard based on its hardness number. The salts in
water will precipitate out when the water is heated and
will cause accelerated lime and scale accumulation on
a heat transfer surface.
Raypak water heaters can operate lime/scale-free
using potable water with a hardness not exceeding 25
grains per gallon. Proper operation is achieved by set-
ting the temperature rise/water flow per the guidelines
in the installation instructions. If the hardness of the
water exceeds the maximum level of 25 grains per gal-
lon special measures must be taken to adjust flow and
temperature rise. Water should be softened to a hard-
ness level no lower than 5 grains per gallon. Water
softened as low as 0 to 1 grain per gallon may be
under-saturated with respect to calcium carbonate
resulting in water that is aggressive and corrosive.
pH of Water
pH is a measure of relative acidity, neutrality or alka-
linity. Dissolved minerals and gases affect water’s pH.
The pH scale ranges from 0 to 14. Water with a pH of
7.0 is considered neutral. Water with a pH lower than
7 is considered acidic. Water with a pH higher than 7
is considered alkaline. A neutral pH (around 7) is desir-
able for most potable water applications. Corrosion
damage and water heater failures resulting from water
pH levels of lower than 6 or higher than 8 are non-war-
rantable. The ideal pH range for water used in a
storage tank or a copper water heater system is 7.2 to
7.8.
Total Dissolved Solids
Total dissolved solids (TDS) is the measure of all min-
erals and solids that are dissolved in the water. The
concentration of total dissolved solids is usually ex-
pressed in parts per million (ppm) as measured in a
NOTE: Chemical imbalance can cause severe
damage to your heater and associated equipment.
Fig. 14: “H” Bypass Setting
NOTE: There are 2 separate drains on the MVB
that must BOTH be drained to protect the heat
exchanger. These are both accessible by removing
the lower front door from the heater. Drain any
piping of all water that may experience below-
freezing temperatures.