50
40
IND GUIDE INST 10-11
HHIC REF T11/0027BRev8
INDUSTRY GUIDANCE FOR INSTALLERS ON CONDENSATE
DRAINAGE PIPE INSTALLATION
This guidance is endorsed by HHIC members.
1. BACKGROUND
During recent winters the UK has experienced prolonged spells of extremely cold weather -
down to minus 20
o
C and below in many areas. This resulted in a significant increase in the
number of calls to boiler manufacturers and heating engineers from householders with
condensing (high efficiency) boilers where the condensate drainage pipe had frozen and
become blocked with ice, causing the boiler to shut down. In the vast majority of cases such
problems occur where the condensate drainage pipe is located externally to the building for
some part of its length.
British Standards, Building Regulations etc. currently allow condensate drainage pipes to be
run either internally or externally, or a combination of these. These documents give guidance
on how to install the pipes in order to reduce the possibility of freezing. However this
guidance may not be sufficient to prevent freezing in extreme conditions - with widespread
and prolonged very low temperatures.
In view of the possibility that UK weather patterns will show more “extremes” in future due to
the effects of global climate change, the following guidance updates previous
recommendations on condensate drainage pipe installation. All other technical requirements
for condensate drain installation given in British Standard BS 6798:2009, or in boiler
manufacturers
’
installation instructions should still be followed.
2. REVISED GUIDANCE ON CONDENSATE DRAINAGE PIPE INSTALLATION
Where a new or replacement boiler is being installed, access to an in
ternal “gravity
discharge” termination
should be one of the main factors considered when determining
potential boiler locations, so that the condensate drainage pipe can be terminated as
recommended below. On an existing installation, the guidance below should also be
followed if work is carried out
to “upgrade” the condensate drain
age system to reduce the
risk of freezing in extreme conditions.
Internal condensate drainage pipework must be a minimum of 19mm ID (typically 22mm OD)
plastic pipe an
d this should “fall” at least 45
mm per metre
away
from the boiler, taking the
shortest practicable route to the termination point.
In order to minimise the risk of freezing during prolonged very cold spells, one of the
following methods of terminating condensate drainage pipe should be adopted -
8
APPENDIX 1 (GUIDANCE HHIC)
40
IND GUIDE INST 10-11
HHIC REF T11/0027BRev8
INDUSTRY GUIDANCE FOR INSTALLERS ON CONDENSATE
DRAINAGE PIPE INSTALLATION
This guidance is endorsed by HHIC members.
1. BACKGROUND
During recent winters the UK has experienced prolonged spells of extremely cold weather -
down to minus 20
o
C and below in many areas. This resulted in a significant increase in the
number of calls to boiler manufacturers and heating engineers from householders with
condensing (high efficiency) boilers where the condensate drainage pipe had frozen and
become blocked with ice, causing the boiler to shut down. In the vast majority of cases such
problems occur where the condensate drainage pipe is located externally to the building for
some part of its length.
British Standards, Building Regulations etc. currently allow condensate drainage pipes to be
run either internally or externally, or a combination of these. These documents give guidance
on how to install the pipes in order to reduce the possibility of freezing. However this
guidance may not be sufficient to prevent freezing in extreme conditions - with widespread
and prolonged very low temperatures.
In view of the possibility that UK weather patterns will show more “extremes” in future due to
the effects of global climate change, the following guidance updates previous
recommendations on condensate drainage pipe installation. All other technical requirements
for condensate drain installation given in British Standard BS 6798:2009, or in boiler
manufacturers
’
installation instructions should still be followed.
2. REVISED GUIDANCE ON CONDENSATE DRAINAGE PIPE INSTALLATION
Where a new or replacement boiler is being installed, access to an in
ternal “gravity
discharge” termination
should be one of the main factors considered when determining
potential boiler locations, so that the condensate drainage pipe can be terminated as
recommended below. On an existing installation, the guidance below should also be
followed if work is carried out
to “upgrade” the condensate drain
age system to reduce the
risk of freezing in extreme conditions.
Internal condensate drainage pipework must be a minimum of 19mm ID (typically 22mm OD)
plastic pipe an
d this should “fall” at least 45
mm per metre
away
from the boiler, taking the
shortest practicable route to the termination point.
In order to minimise the risk of freezing during prolonged very cold spells, one of the
following methods of terminating condensate drainage pipe should be adopted -
8
APPENDIX 1 (GUIDANCE HHIC)
41
IND GUIDE INST 10-11
HHIC REF T11/0027BRev8
2.1 INTERNAL TERMINATION:
Wherever possible, the condensate drainage pipe should be terminated at a suitable internal
foul water discharge point such as (a) an internal soil and vent stack or (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 1, 2(a), 2(b) show appropriate
connection methods.
The possibility of waste pipes freezing downstream of the connection point should be
considered when determining a suitable connection point - e.g. a slightly longer pipe run to
an internal soil stack may be preferable to a shorter run connecting into a kitchen waste pipe
discharging directly through the wall to an external drain.
Where
“gravity discharge” to an internal termination is not physically possible (e.g. the
discharge point is above the appliance location, or access is obstructed by a doorway), or
where very long internal pipe runs would be required to reach a suitable discharge point, the
following measures may be adopted -
2.2 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.
The pump outlet should discharge to a suitable internal foul water discharge point, such as
(a) an internal soil and vent stack or (b) an internal kitchen or bathroom waste pipe, washing
machine waste pipe etc. Figure 3 shows a typical connection method.
A suitable permanent connection to the foul waste pipe should be used and the
manufacturer’s
detailed installation instructions for the pump should be followed.
2.3 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)
.
