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20
11. CONDENSATE
DRAIN
11.1
Where a new or replacement boiler is being installed, access to an
internal “gravity discharge” termination should be one of the main
factors considered when determining potential boiler locations, the
condensate drainage pipe should be terminated as recommended.
11.2
Internal condensate drainage pipework must be a minimum of
19mm ID (typically 22mm OD) plastic pipe and this should “fall”
at least 45mm per metre away from the boiler, taking the shortest
practicable route to the termination point.
11.3
In order to minimise the risk of freezing during prolonged very cold
spells, the condensate drainage pipe should be terminated at a
suitable internal foul water discharge point using either:-
a. an internal soil and vent stack
b. an internal kitchen or bathroom waste pipe, washing machine
waste pipe etc. A suitable permanent connection to the foul
waste pipe should be used. Figures 18 to 20 show appropriate
connection methods.
11.4
USE OF A CONDENSATE PUMP (TO AN INTERNAL
TERMINATION)
:
Condensate can be removed using a proprietary
condensate pump, of a specification recommended by the boiler or
pump manufacturer.
11.5 EXTERNAL
TERMINATION
:
The use of an externally-run condensate
drainage pipe, terminating at a suitable foul water discharge point
or purpose-designed soakaway, may be also be considered;
however if this termination method is chosen then the following
measures should be adopted - The pipe should be run internally
as far as possible before going externally and the pipe diameter
should be increased to a minimum of 30mm ID (typically 32mm
OD) before it passes through the wall. The external run should be
kept as short as possible, taking the most direct and “most vertical”
route possible to the discharge point, with no horizontal sections
in which condensate might collect. The external pipe should be
insulated using suitable waterproof and weatherproof insulation
(“Class O” pipe insulation is suitable for this purpose) .
11.6
The use of fittings, elbows etc should be kept to a minimum and
any internal “burrs” on cut pipework should be removed so that the
internal pipe section is as smooth as possible.
11.7
The customer/householder should be advised that even with the
above measures this type of installation could freeze, and that if this
were to occur then boiler shutdown could result, requiring remedial
action - possibly involving a chargeable engineer call-out.
11.8
Where there are likely to be extremes of temperature or wind-chill, the
use of a proprietary trace-heating system for external condensate
drainage pipework, incorporating an external frost thermostat,
should therefore be considered. If such a system is used then the
installation instructions of the trace heating manufacturer and any
specific recommendations regarding pipe diameter, insulation,
etc. should be followed. All other relevant guidance on condensate
drainage pipe installation should also be followed.
11.9
If an external soil/vent stack is used as the external termination then
the connection method shown in Figure x should be used, together
with the measures on insulation etc. as described above and shown
in the diagram.
11.10
Where the condensate drain pipe terminates in a purpose-designed
soakaway (see BS 6798 or boiler installation manual for soakaway
design requirements) any above-ground section of condensate
drainage pipe should be run and insulated as described above.
Figure 7 shows a suitable connection method. (see Figure 20).
11.11 UNHEATED
INTERNAL
AREAS:
Internal condensate drainage
pipes run in unheated areas such as lofts, basements and garages
should be treated as external pipe.
DRAIN
OUTSIDE
GROUND
LEVEL
25mm
75mm
100mm
MINIMUM INTERNAL
DIAMETER 19mm
VISIBLE
AIR BREAK
WATER &
WEATHERPROOF
INSULATION
SINK, BASIN, BATH
OR SHOWER
MINIMUM
INTERNAL
DIAMETER
30mm
PIPE SIZE
TRANSITION
75mm TRAP
NOTE:-
Visible air break and trap
not required if there is a trap
with a minimum condensate
seal of 75 mm incorporated
into the boiler. In this case the
100 mm is measured to the
trap in the boiler.
NOTE:-
Open end of condensate drainage pipe direct
into gully 25 mm min below grating but above
water level; end cut at 45 °
OUTSIDE
GROUND
LEVEL
75mm
100mm
MINIMUM INTERNAL
DIAMETER 30mm
PIPE SIZE
TRANSITION
SINK, BASIN, BATH OR
SHOWER WASTE TRAP
NOTE:-
Open end of condensate drainage pipe direct
into gully 25 mm min below grating but above
water level; end cut at 45 °
DRAIN
25mm
WATER &
WEATHERPROOF
INSULATION
VISIBLE AIR BREAK
AT PLUG HOLE
MINIMUM INTERNAL
DIAMETER 19mm
MINIMUM
INTERNAL
DIAMETER 19mm
MINIMUM TRAP
VISIBLE
AIR BREAK
WATER &
WEATHERPROOF
INSULATION
MINIMUM INTERNAL
DIAMETER 30mm
PIPE SIZE
TRANSITION
NOTE:-
Visible air break and trap not
required if there is a trap with
a minimum condensate seal
of 38mm incorporated into
the boiler
NOTE:-
Open end of condensate drainage
pipe direct into gully 25 mm min
below grating but above
water level; end cut at 45°
DRAIN
OUTSIDE
GROUND
LEVEL
25mm
38mm
CONDENSE
DISCHARGE
PIPE FROM
BOILER
û
25mm
û
300mm
û
500mm
PIPE SIZE
TRANSITION
NOTE:-
Ground (this section of
the condensate drainage
pipe may be run either
above or below ground
level; End cut at 45°.
Hole depth
400mm minimum
By 300mm
Diameter
BOTTOM OF
TUBE SEALED
DIAMETER
100mm MINIMUM
PLASTIC TUBE
WATER &
WEATHERPROOF
INSULATION
EXTERNAL
WALL
GROUND LEVEL
LIMESTONE
CHIPPINGS
Two rows of three
12mm holes at 25mm centres,
50mm from bottom of tube
And facing away from house
MINIMUM
INTERNAL
DIAMETER 30mm
FIGURE 17. DOWNSTREAM CONNECTION
FOR SINK, BASIN, BATH OR SHOWER TRAP
FIGURE 18. UPSTREAM CONNECTION
FOR SINK, BASIN, BATH OR SHOWER TRAP
FIGURE 19.
DRAIN, GULLY OR RAINWATER
FIGURE 20.
PURPOSE DESIGNED SOAKAWAY
