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CONNECTIONS – PLUMBING
33
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
required if the saturation index is greater than +0.4 (refer to “Water Supplies”
on page 13).
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 30). A copper drain line must be fitted to the expansion control valve
(refer to "Relief Valve Drain" on page 33).
The valve, if installed within 500 mm of the water heater, must be insulated with
closed cell polymer insulation or similar (minimum thickness 9 mm) and the
insulation installed so as not to impede the operation of the valve. The
insulation must be weatherproof and UV resistant if exposed.
RELIEF VALVE DRAIN
DN15 copper drain lines must be fitted to the temperature pressure relief valve
and expansion control valve (if one is installed) to carry the discharge clear of
the water heater. Connect the drain lines to the valves using disconnection
unions. The drain line from the valve to the point of discharge should be as
short as possible, have a continuous fall all the way from the water heater to
the discharge outlet and have no tap, valves or other restrictions in the pipe
work. A drain line from a relief valve must comply with the requirements of
AS/NZS 3500.4.
A drain line must be no longer than 9 metres with no more than three bends
greater than 45° before discharging at an outlet or air break. The maximum
length of 9 metres for a drain line is reduced by 1 metre for each additional
bend required of greater than 45°, up to a maximum of three additional bends.
Where the distance to the point of final discharge exceeds this length, the drain
line can discharge into a tundish.
Subject to local regulatory authority approval, the drain lines from the
temperature pressure relief valve and expansion control valve from an
individual water heater may be interconnected.
The outlet of a drain line must be in such a position that flow out of the pipe can
be easily seen, but arranged so discharge will not cause injury, damage or
nuisance. The termination point of a drain line must comply with the
requirements of AS/NZS 3500.4. Drain lines must not discharge into a safe
tray.
In locations where water pipes are prone to freezing, drain lines must be
insulated, must not exceed 300 mm in length and are to discharge into a
tundish through an air gap of between 75 mm and 150 mm.
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