Rheem 180 Owner's Manual And Installation Instructions page 20

WATER SUPPLIES
SATURATION INDEX
The saturation index is used as a measure of the water's corrosive or scaling properties. The saturation index
figures stated are calculated using a water temperature of 80°C.
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 the Rheem warranty does not apply to a copper
sheathed heating unit or a solar collector in a direct solar water heater system. A corrosion resistant heating
and an indirect solar water heater must be used unit must be used for the Rheem warranty to apply to the
heating unit and solar collector. This water heater is supplied fitted with a corrosion resistant 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 the Rheem warranty to apply to the
temperature pressure relief valve and water heater cylinder. Solar collectors in a direct solar water heater
system should be covered when the water heater is not intended to be used for more than two weeks.
Where the saturation index exceeds +0.80, the Rheem warranty does not apply to a standard watts density
heating unit or a solar collector in a direct solar water heater system. A low watts density heating unit or an
indirect solar water heater must be used for the Rheem warranty to apply to the heating unit or solar collector.
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
position of the expansion control valve.
Contact Rheem Service or their nearest Accredited Service Agent if a replacement heating unit is required.
-1.0
very corrosive
on page 20. Refer to the
SATURATION INDEX (SI)
SOLAR WATER HEATERS WITH ELECTRIC HEATING UNIT
WITHIN WARRANTY
SPECIFICATION
SATURATION INDEX
(calculated @ 80°C water temperature)
corrosive
cold water connection detail on page
0 +0.4
scaling very scaling
20
56 for the
+0.8