Page 16
DESIGN
SY
STEM DET
AILS
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 sufficient for a small
1bathroom dwelling (depending upon the flow rate available), but the minimum
recommended size for new dwellings is 22mm (25mm MDPE). For the BMA 245
OV SOL model and above 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 the same size pipework as the incoming mains supply. The cold main and
hot draw-off should also be run in 22mm as far as the branch to the bath tap.
3. The final 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 and before the
pressure reducing valve (if fitted).
5. We would recommend that best results for a balanced system are achieved
by fitting appropriate flow 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
flow regulators are provided in Appendix A.
Note: If manifolds (available as an optional extra) are being used suitable flow
regulators are automatically provided in the manifold and do not need to be
provided at each outlet - See Appendix B for further details.
All the recommendations with regard to pipework systems in this manual are generally
based on the use of BS/EN Standard copper pipework and fittings.
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 confirms that the design criteria of the new system is at least equivalent
to the use of BS/EN Standard copper pipework and fittings or the pipework sizes are
increased accordingly.
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. This 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.
If it is proposed to use a ‘whole body’ or similar
shower with a number of high flow/pressure
outlets please check suitability with the Gledhill
Technical Department before installation.
The hot water supply to a shower-mixing
valve should be fed wherever practical directly
from the BoilerMate A-Class OV SOL or be the
first 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 flushing 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 time before hot water is
available at the tap may be unacceptable. In
these circumstances, you may wish to consider
using trace heating to the hot water pipework
such as the Raychem HWAT system. 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.
