Rheem Optima Owner's Manual And Installation Instructions page 13

WATER SUPPLIES
SATURATION INDEX
The saturation index is used as a measure of the water‟s corrosive or scaling
properties.
In a corrosive water supply, the water can attack copper parts and cause them
to fail. Where the saturation index is less than –1.0, the water is very corrosive
and warranty does not apply to a copper sheathed heating unit. A corrosion
resistant heating unit must be used for warranty to apply to the heating unit.
In a scaling water supply calcium carbonate is deposited out of the water onto
any hot metallic surface. Where the saturation index exceeds +0.40, the water
is very scaling. An expansion control valve must be fitted on the cold water line
after the non-return valve to protect and for warranty to apply to the
temperature pressure relief valve and water heater cylinder.
Where the saturation index exceeds +0.80, warranty does not apply to a
standard watts density heating unit. A low watts density heating unit must be
used for warranty to apply to the heating unit.
Water which is scaling may be treated with a water softening device to reduce
the saturation index of the water.
Refer to the Saturation Index chart on page 13. Refer to the cold water
connection detail on page 27 for the position of the expansion control valve.
Contact Rheem Service Centre if a replacement heating unit is required.
SATURATION INDEX (SI)
ELECTRIC WATER HEATERS
WITHIN WARRANTY
SPECIFICATION
-1.0 0 +0.4 +0.8
SATURATION INDEX
(calculated @ 80°C water temperature)
scaling
very corrosive corrosive very scaling
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