Rheem 491 Owner's Manual And Installation Instructions page 13

Note: When the electrical supply is switched back on, the water heater will take
some time to reheat the water. Depending upon the power supply connection,
hot water may not be available until the next day.
HOW DO I KNOW IF THE WATER HEATER IS INSTALLED CORRECTLY?
Installation requirements are shown on pages 24 to 31. The water heater must
be installed:

by a qualified person, and

in accordance with the installation instructions, and

to conform to Clauses G12 and H1 of the New Zealand Building Code, and

in compliance with Standards AS/NZS 3500.4, AS/NZS 3000 and all local
codes and regulatory authority requirements.
DOES THE WATER CHEMISTRY AFFECT THE WATER HEATER?
The water heater is suitable for most public water supplies, however some water
chemistries may have detrimental effects on the water heater, its components
and fittings. Refer to "Water Supplies" on page 17.
If you are in a known harsh water area or you are not sure of your water
chemistry, have your water checked against the conditions described on
pages 17 to 20.
HOW LONG WILL THE WATER HEATER LAST?
The water heater is supported by a manufacturer's warranty (refer to page 4).
There are a number of factors that will affect the length of service the water
heater will provide. These include but are not limited to the water chemistry, the
water pressure, the water temperature (inlet and outlet) and the water usage
pattern. Refer to "Precautions" on page 12.
ABOUT YOUR WATER HEATER
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