Rheem Optima Owner's Manual And Installation Instructions page 14

WATER SUPPLIES
CHANGE OF WATER SUPPLY
The changing or alternating from one water supply to another can have a
detrimental effect on the operation and / or life expectation of a water heater
cylinder, a temperature pressure relief valve and a heating unit.
Where there is a changeover from one water supply to another, e.g. a rainwater
tank supply, bore water supply, desalinated water supply, public reticulated
water supply or water brought in from another supply, then water chemistry
information should be sought from the supplier or it should be tested to ensure
the water supply meets the requirements given in these guidelines for warranty
to apply.
SUMMARY OF WATER CHEMISTRY ADVICE AFFECTING WARRANTY
The warranty of this water heater does not apply on the components listed
below if the water heater is connected at any time to a water supply with water
chemistry of:
Water Chemistry
Total Dissolved Solids (TDS) > 2500 mg/L
Total Dissolved Solids (TDS)
not suitable for anode type
Saturation Index (SI) < -1.0
Saturation Index (SI) > +0.4
(if expansion control valve is not fitted)
Saturation Index (SI) > +0.8
Component
water heater cylinder
water heater cylinder
copper sheathed heating unit
water heater cylinder
temperature pressure relief valve
standard watts density heating unit
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