SYSTEM DESIGN
6
HOT AND COLD WATER SERVICES
A schematic layout of the hot and cold water services in
a typical small dwelling is shown in Figure 2.1.
PulsaCoil III will operate at mains pressures as low as
1 bar and as high as 8 bar although the preferred range
is 2-3 bar. It is also important to check that all other
equipment and components in the hot and cold water
system are capable of accepting the mains pressure
available to the property.
If the mains pressure can rise above the maximum
working pressure of any items of equipment or
component to be fitted a suitable pressure limiting
(reducing) valve will be required.
For properties with a higher supply pressure than 8 bar
it is recommended that a pressure limiting valve is
fitted, set at 3 bar.
PulsaCoil III is WBS approved. A non-return valve is not
required. Should ancillary equipment fitted in the supply
to the PulsaCoil require a non-return valve, then this valve
must be fitted directly after the branch to the drinking
water tap (kitchen sink). See Figure 1.1 for details.
Note:
The hot and cold water distribution pipework should
be designed and installed to prevent heating of the cold
distribution pipe.
Taps and Valves
Aerated taps are recommended for all mains pressure
systems to prevent splashing.
Pipe Sizing
To achieve even distribution of the available supply of
hot and cold water, it is important in any mains pressure
system that the distribution pipes in a dwelling should
be sized in accordance with BS6700. This is particularly
important in a large property or one with more than one
bathroom. However the following rule of thumb guide lines
should be adequate for most typical property types:
a)
A 15mm copper or equivalent external service may
be sufficient for smaller 1 bathroom dwellings
(depending upon the flow rate available), but the
minimum size for larger dwellings must be 22mm
(25mm MDPE).
b)
The internal cold feed from the main stop tap to the
PulsaCoil should be run in 22mm pipe. The hot draw-
off should also be run in 22mm as far as the branch
to the bath tap.
c )
The final branches to the hand basins and sinks
should be in 10mm and to the shower in 15mm.
d)
The final branches to taps in existing properties,
which are in 15mm,
should be restricted
to balance
the flow to each outlet.
e)
Best results for a balanced system are achieved by
fitting appropriate flow regulators to each hot and
cold outlet (see Appendix 1).
f)
For properties where the inlet pressure is high and
the flow rates may exceed 30 l/min at any bath hot
tap the installer must fit a lockshield pattern gate
valve at the cold inlet to the appliance. This should
then be adjusted to restrict the maximum flow rate
to 30 l/min.
On the odd occasion it is felt necessary to provide a
secondary circulation. We would recommend the
use of Raychem HWAT Plus or similar self regulating
trace heating to maintain the temperature in the hot
water distribution system. The system must be
installed and commissioned fully in accordance with
the manufacturers instructions.
Showers
a)
Any type of shower mixing valve can be used as
long as both the hot and cold supplies are mains
fed. However
PRESSURE COMPENSATING
shower
mixing valves are proven to give better control when
more than one fitting are open simultaneously and
are therefore
STRONGLY RECOMMENDED.
Thermostatic versions are preferable.
b)
The hot water supply to a shower mixing valve should,
wherever practical, be fed directly from the PulsaCoil
III or be the first draw-off point on the hot circuit.
c )
The cold supply to a shower mixing valve should be
fed directly from the rising mains via an independent
branch.
d)
Fixed head type showers:
No back-syphonage
arrangements are necessary.
e)
Loose or flexible head type showers:
If a loose
head shower with a flexible hose is used over a bath
then: -
•
The
hose must be fixed so that the head cannot
fall closer than 25mm above the top edge of the
bath as specified in Model Byelaw 16 of the Water
Supply Byelaws.
Or
•
The shower must incorporate or be fitted with an
acceptable means of back-syphonage protection
in accordance with the Model Water Byelaws.
Bidets
a)
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.
b)
It must not include either an ascending spray or
provision to attach a hand spray.
