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15
7.0 SITE REQUIREMENTS
Publication No. 5111811
7.6 Condensate Drain
FAILURE TO INSTALL THE CONDENSATE DISCHARGE
PIPEWORK CORRECTLY WILL AFFECT THE RELIABLE
OPERATION OF THE BOILER
The condensate discharge pipe MUST NOT RISE at any
point along its length. There MUST be a fall of AT LEAST
2.5° (50mm per metre) along the entire run.
1. The condensate outlet terminates in a 1” BSP nut and
seal for the connection of 21.5mm (
3
/
4
in) plastic overflow
pipe which should generally discharge internally into the
household drainage system. If this is not possible,
discharge into an outside drain is acceptable.
2. Ensure the discharge of condensate complies with any
national or local regulations in force.
BS 6798:2000 & Part H1 of the Building Regulations
give further guidance.
3. The discharge pipe should be run in a proprietary drain
pipe material e.g. PVC, PVC-U, ABS, PVC-C or PP.
4. Metal pipework is NOT suitable for use in condensate
discharge systems.
5. The pipe should be a minimum of 21.5mm diameter
and must be supported using suitably spaced clips to
prevent sagging.
6. Any pipe fitted externally must not exceed 3 metres.
7. Any condensate discharge pipework external to the
building (or in an unheated part of it e.g. garage) must
be insulated to protect against frost. It is also
recommended that the pipe diameter is increased to
32mm.
8. If the boiler is fitted in an unheated location the entire
condensate discharge pipe should be treated as an
external run.
9. In all cases discharge pipe must be installed to aid
disposal of the condensate. To reduce the risk of
condensate being trapped, as few bends and fittings as
possible should be used.
10. When discharging condensate into a soil stack or
waste pipe the effects of existing plumbing must be
considered. If soil pipes or waste pipes are subjected to
internal pressure fluctuations when WC's are flushed or
sinks emptied then back-pressure may force water out of
the boiler trap and cause appliance lockout.
Examples are shown of the following methods of
termination:-
i) to an internal soil & vent pipe
ii) via an internal discharge branch (e.g. sink waste)
iii) to a drain or gully
iv) to a purpose made soakaway
Boiler
2.5° Minimum fall
Termination to an internal soil
and vent pipe
450mm min
Boiler
2.5° Minimum fall
External termination via internal
discharge branch
e.g sink waste - downstream
Sink
Pipe must terminate
above water level but
below surrounding
surface
Boiler
Pipe must terminate
above water level but
below surrounding
surface
2.5° Minimum fall
External termination to a drain or gully
Boiler
500mm min
2.5° Minimum fall
External termination to a purpose
made soak-away
Holes in the soak-away
must face away from the
building
50mm per metre of pipe run
50mm per metre of pipe run
50mm per metre of pipe run
50mm per metre of pipe run