Operating instructions
31 
WATER SUPPLIES 
This water heater must be installed in accordance with this advice to be covered by the Rheem 
warranty. 
This water heater is manufactured to suit the water conditions of most public reticulated water supplies. 
However, there are some known water chemistries which can have detrimental effects on the water heater 
and its operation and / or life expectancy. If you are unsure of your water chemistry, you may be able to 
obtain information from your local water supply authority. This water heater should only be connected to a 
water supply which complies with these guidelines for the Rheem warranty to apply. 
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 heat exchanger in a continuous flow water heater. 
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 the Rheem warranty to apply. 
SATURATION INDEX 
The saturation index (SI) 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 the Rheem warranty does not apply to a copper heat 
exchanger in a continuous flow water heater. 
In a scaling water supply calcium carbonate is deposited out of the water onto any hot metallic surface. 
Where the saturation index exceeds +0.80, the Rheem warranty does not apply to a copper heat exchanger 
in a continuous flow water heater. 
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 31. 










