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Hot and Cold Water System
Pipe Sizing / Materials
To achieve even distribution of the available supply of hot and cold water, it is
important in any mains pressure system, that the piping in a dwelling should be
sized in accordance with BS 6700. This is particularly important in a large property
with more than one bathroom.
However, the following rule of thumb guide lines should be adequate for most smaller
property types as long as water pressures are within the recommended range of 2-3
bar.
1. A 15mm copper or equivalent external service may be suffi cient for a small
1bathroom dwelling (depending upon the fl ow rate available), but the minimum
recommended size for new dwellings is 22mm (25mm MDPE). For the BMBP 225
model we recommend a 28mm (32mm MDPE) supply pipe.
2. The internal cold feed from the main incoming stop tap to the BoilerMate
should be run in 22mm pipe. The cold main and hot draw-off should also
be run in 22mm as far as the branch to the bath tap.
3. The fi nal branches to the hand basins and sinks should be in 10mm and to
the baths and showers in 15mm. (1 metre minimum)
4. If an external hose tap is provided this should be branched in 15mm pipework
from the cold pipework as near to the incoming mains as possible.
5. We would recommend that best results for a balanced system are achieved
by fi tting appropriate fl ow regulators to each hot and cold outlet. This is
particularly relevant where the water pressures are above the recommended
water pressure range of 2-3 bar, or the dwelling is 3 storey. Details of suitable
fl ow regulators are provided in Appendix.
All the recommendations with regard to pipework systems in this manual are generally
based on the use of BS/EN Standard copper pipework and fi ttings.
However, we are happy that plastic pipework systems can be used in place of copper
internally as long as the chosen system is recommended for use on domestic hot and
cold water systems by the manufacturer and is installed fully in accordance with their
recommendations.
It is also essential that if an alternative pipework material/system is chosen the
manufacturer confi rms that the design criteria of the new system is at least equivalent
to the use of BS/EN Standard copper pipework and fi ttings.
Taps/Shower Fittings
Aerated taps are recommended to prevent splashing.
Any type of shower mixing valve can be used as long as both the hot and cold
supplies are mains fed. However, all mains pressure systems are subject to
dynamic changes particularly when other hot and cold taps/showers are opened
and closed, which will cause changes in the water temperature at mixed water
outlets such as showers. For this reason and because these are now no more
expensive than a manual shower we strongly recommend the use of thermostatic
showers with this appliance. These must be used in 3 storey properties where
the impact on pressure/temperature of opening another tap in the system is
greater than normal.
The shower head provided must also be suitable for mains pressure supplies.
However, if it is proposed to use a 'whole body' or similar shower with a number of
high fl ow/pressure outlets please discuss with the Gledhill technical department.
The hot water supply to a shower-mixing valve should be fed wherever practical
directly from the BoilerMate BP or be the fi rst draw-off point on the hot circuit. The
cold supply to a shower-mixing valve should
wherever practical be fed directly from the
rising mains via an independent branch. The
shower must incorporate or be fitted with
the necessary check valves to provide back-
syphonage protection in accordance with the
Water Regulations.
The supply of hot and cold mains water directly
to a bidet is permitted provided that it is of the
over-rim fl ushing type and that a type 'A' air
gap is incorporated.
Hot and Cold Water System.
If the length of the hot water draw off
pipework is excessive the delivery time may
be unacceptable before hot water is available at
the tap, you may wish to consider using either
trace heating to the hot water pipework such
as the Raychem HWAT system or secondary
circulation. Please consult Gledhill Technical
Department for further details.
It is important that the cold water pipework
is adequately separated/protected from any
heating/hot water pipework to ensure that
the water remains cold and of drinking water
quality.
Page 11
DESIGN
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