CONNECTIONS
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PLUMBING
37
RELIEF VALVE DRAIN
DN15 copper drain lines must be fitted to the temperature pressure relief valve and expansion control valve
(if one is installed). 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.
If a drain line discharges into a tundish, the drain line from the tundish must be not less than DN20. The
drain line from a tundish must meet the same requirements as for a drain line from a relief valve.
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.
BLEED VALVE DRAIN
A copper drain line must be fitted to the bleed valve to carry the discharge clear of the water heater and solar
control unit. Connect the drain line to the bleed valve using a disconnection union. The pipe work from the
bleed valve to the drain should be as short as possible and fall all the way from the valve 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 water discharge will not cause injury, damage, nuisance or splashing. The
water discharged may be of a high temperature under certain conditions. The drain line must be fully
insulated with closed cell polymer insulation or similar (minimum thickness 13 mm). The insulation must be
weatherproof and UV resistant if exposed.
