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PLUMBING - CONNECTIONS
RELIEF VALVE DRAIN
DN15 copper drain lines must be fitted to the PTR and ECV 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 continuously downward 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 G12/AS1
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 the provisions in G12/AS1, 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 G12/AS1 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.
318457 Rev D Issued: 15/11/18
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