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CONNECTIONS – PLUMBING
22
RELIEF VALVE DRAIN
A copper drain line must be fitted to the relief valve to carry the discharge clear
of the water heater. Connect the drain line to the relief valve using a
disconnection union. The pipe work from the relief valve to the drain should be
as short as possible and fall all the way from the water heater with no
restrictions. It should have no more than three right angle bends in it. Use
DN15 pipe.
The outlet of the drain line must be in such a position that flow out of the pipe
can be easily seen (refer to AS/NZS 3500.4) - but arranged so hot water
discharge will not cause injury, damage or nuisance. The drain line must
discharge at an outlet or air break not more than 9 metres from the relief valve.
In locations where water pipes are prone to freezing, the drain line must be
insulated and not exceed 300 mm in length. In this instance, the drain line is to
discharge into a tundish through an air gap of between 75 mm and 150 mm.
Warning: As the function of the temperature pressure relief valve on this water
heater is to discharge high temperature water under certain conditions, it is
strongly recommended the pipe work downstream of the relief valve be capable
of carrying water exceeding 93°C. Failure to observe this precaution may result
in damage to pipe work and property.
EXPANSION CONTROL VALVE
Local regulations may make it mandatory to install an expansion control valve
(ECV) in the cold water line to the water heater. In other areas, an ECV is not
required unless the saturation index is greater than +0.4 (refer to “Water
Supplies” on page 30). However, an ECV may be needed in a corrosive water
area where there are sufficient quantities of silica dissolved in the water.
The expansion control valve must always be installed after the non return valve
and be the last valve installed prior to the water heater (refer to diagram on
page 20). A copper drain line must be run separately from the drain of the relief
valve.