Hot And Cold Water Supply Pipe Lengths - gledhill TORRENT DIRECT Design, Installation & Servicing Instructions

3.5 HOT AND COLD WATER SUPPLY PIPE LENGTHS (DEADLEG VOLUMES)
(a) If the length of the hot water draw-off pipework is excessive and the delivery time will be
more than 60 seconds before hot water is available at the tap, you may wish to consider
using trace heating to the hot water pipework such as the Raychem HWAT system.
Also a conventional pumped secondary circulation system (figure 3.2) can be used with
any model of the Torrent.
(b) It is important that the cold water pipework is adequately separated and protected from
any heating from the hot water pipework to ensure that the water remains cold and of
drinking water quality.
3.6 WATER FLOW NOISE AND WATER HAMMER
(a) The water flow noise from the pipework is generally caused when the vibration/oscillation
of pipe surface is induced by the water flowing through it. The water flow noise do not
become significant provided the water velocity is kept below 3 m/s.
(b) The water hammer is a pulsating type of noise which may be heard from the pipework
installation or the hot water appliance. This noise is mainly caused by shock waves which
are set up when water which is flowing at high velocity is suddenly stopped e.g. by rapidly
closing tap or an instantaneously closing automatic control valve. Pumped water supplies
in a building can create the water hammer if provision for absorbing the shock wave is not
made during the design stage.
(c) Shock pressures in the pipework supplied at high pressures can be reduced to acceptable
limits by fitting water surge arrestors i.e. hydro-pneumatic accumulators in the pipe line at
suitable points
The comprehensive sizing procedures are given in 'Plumbing Engineering Services Design
Guide' and other such publications. As a rule of thumb for total pipe runs up to 50m and
water pressure up to 4.0 bar; the following sizes of expansion vessels charged to the
mains pressure may eliminate the water hammer
0.15 litre vessel for pipework in 15mm
0.25 litre vessel for pipework in 22mm
0.40 litre vessel for pipework in 28mm
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DESIGN