Rheem 180 Owner's Manual And Installation Instructions page 21

SUMMARY OF WATER CHEMISTRY ADVICE AFFECTING WARRANTY
The water heater and its components are not suitable for certain water chemistries. Those chemistries are
listed below. If the water heater is connected at any time to a water supply with the following water chemistry,
the Rheem warranty will not cover any resultant faults on the components listed below:
Water Chemistry
Chloride > 250 mg/L
pH < 6.0
Saturation Index (SI) < -1.0
Saturation Index (SI) > +0.4
(if an expansion control valve is not fitted)
Saturation Index (SI) > +0.8
Component
water heater cylinder and heat exchanger
water heater cylinder and heat exchanger
solar collector in a direct system
copper sheathed heating unit
water heater cylinder and heat exchanger
temperature pressure relief valve
solar collector in a direct system
standard watts density heating unit
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WATER SUPPLIES