Rheem 874 Owner's Manual And Installation Instructions page 54

PIPE SIZES
The pipe sizing for hot water supply systems should be carried out by persons competent to do so, choosing
the most suitable pipe size to ensure adequate flow for each individual application. Reference to the
technical specifications of the water heater and local regulatory authority requirements must be made.
To achieve true mains pressure operation, the cold water line to the water heater should be the same size or
bigger than the hot water line from the water heater.
The minimum recommended cold pipe or solar preheat pipe and hot pipe size is DN20.
IN-SERIES BOOST WATER HEATER
The pipe work between the solar storage tank (if one is installed) and the gas booster water heater has a
minimum recommended pipe size of DN20, MUST BE of copper and be fully insulated in accordance with
the requirements of AS/NZS 3500.4. The insulation must be weatherproof and UV resistant if exposed. The
insulation must be fitted up to the connections on both the solar storage tank and the gas booster water
heater. A full flow isolation valve must be installed on the water line to the gas booster water heater.
GAS INLET
The gas connection is made at the underside of the water heater. The pipe work must be cleared of foreign
matter before connection and purged before attempting to operate the water heater. An isolation valve and
disconnection union must be installed to allow servicing and removal of the water heater (refer to the
diagram on page 53).
Note: Refer to the Gas Installations Standard NZS 5261 or AS/NZS 5601 for the correct method of sizing the
gas supply pipe to the water heater. The pipe size selection must take into account the high gas input of this
water heater (refer to table on page 49) as well as all of the other gas appliances in the premises.
Warning: Always isolate the water heater before pressure testing the gas supply system. Disconnect the
water heater after the isolation valve to prevent the risk of serious damage to the gas control. Warranty does
not cover damage of any nature resulting from failure to observe this precaution. Refer to rating label for gas
types and pressures.
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