Rheem Water Star Owner's Manual And Installation Instructions page 24

CONNECTIONS – PLUMBING
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.
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.
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