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7.0 Site Requirements
© Baxi Heating UK Ltd 2011
7.7 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 will accept 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 & 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. It is advisable to keep the condensate pipe internal.
7. External runs greater than 3 metres or runs in cold areas
should use 32mm waste pipe.
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 - Fig. 13
ii) via an internal discharge branch (e.g. sink waste) - Fig. 14
iii) to a drain or gully - Fig. 15
iv) to a purpose made soakaway - Fig. 16
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
Termination to a drain or gully
Boiler
500mm min
2.5° Minimum fall
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
Fig. 13
Fig. 14
Fig. 15
Fig. 16