NOTE: A discharge pipe the full size of the relief
valve outlet will be shown connected to the outlet
and shown on the drawings terminated at a safe
location. The discharge pipe should not be directly
connected to the drainage system and will conform to
the requirements of the International Plumbing Code
(for commercial and industrial hot water heaters
ASME BPVC SEC IV also applies).
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Valves shall not be installed between a relief valve and its water heater
or storage tank. The relief valves shall be installed where the valve
actuator comes in contact with the hottest water in the heater or tank.
Whenever possible, the valve shall be installed directly in a tapping in
the tank or heater. When heaters are not provided with a relief valve
tapping, the valve shall be installed in the hot water outlet piping. A
vacuum relief valve shall be provided on the cold water supply line to the
hot water storage tank or water heater and mounted above and within 150 mm
6 inches of the tank or water heater.
3.18.2
Gas and Oil Fired Water Heaters
Installation shall conform to NFPA 54 for gas fired and NFPA 31 for oil
fired. [A phenolic resin coating shall be provided.]
3.18.3
Storage Water Heaters
Storage water heaters that are not equipped with integral heat traps and
having vertical pipe risers shall be installed with heat traps directly on
both the inlet and outlets. Circulating systems need not have heat traps
installed. An acceptable heat trap may be a piping arrangement such as
elbows connected so that the inlet and outlet piping make vertically upward
runs of not less than 600 mm 24 inches just before turning downward or
directly horizontal into the water heater's inlet and outlet fittings.
Commercially available heat traps, specifically designed by the
manufacturer for the purpose of effectively restricting the natural
tendency of hot water to rise through vertical inlet and outlet piping
during standby periods, may also be approved. [A phenolic resin coating
shall be provided.]
3.18.4
Heat Traps
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NOTE: Piping arrangement for the heat trap should
be shown on the drawings.
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Piping to and from each water heater and hot water storage tank shall be
routed horizontally or downward a minimum of 600 mm 2 feet before turning
in an upward direction.
3.18.5
Connections to Water Heaters
Connections to water heaters and metallic pipe shall be made with
dielectric unions or flanges.
3.18.6
Expansion Tank
A precharged expansion tank shall be installed on the cold water supply
SECTION 15405A
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