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PLUMBING CONNECTION
WINTER 2016
being experienced within more complex piping systems
in areas such as Health Care and Hospitality irrespective
of the pipe material. Occasionally these are contained to
warm water delivery lines from Thermostatic Mixing Valves
(TMV’s) to fixture outlet, however at various sites noise is
also occurring in some cold water lines or in areas where no
TMV’s are installed.
TMV’s require the mandatory inclusion of a non-return
valve as an integral part of the product to prevent cross
connection of heated and cold water supply. Trials with
different TMV’s, removal of the TMV’s, lowering the pressure
and changing the end of line tapware generally did not
eliminate the issue leading to the conclusion that it is
primarily related to a combination of factors including pipe
material choice, sizing and velocity issues.
One other issue has arisen being the possibility of Reverse
Water Hammer. This is where a tap or control valve is located
some distance away from the end of the pipe. As the tap
or control valve closes, the flowing water causes a vacuum
immediately after the device. The vacuum may suddenly
reverse the water flow, causing a vibration and loud banging
noise. To minimise this occurrence, the pipe work after the
device should be larger thereby reducing the water velocity
in the pipe on the outlet side.
STEPS TO MINIMISE NOISE ANDWATER HAMMER
∫ Design pipe work so that the velocity is no greater than 1.5
m/sec.
∫ Ensure that when changing materials or designs that the
internal diameter of alternate material is the same, or
larger, than the design criteria.
∫ Keep the pressure in the system well below 500 kPa with
pressure limiting valves.
∫ Make sure that all pipe work is secured by clips at the
correct spacing for the pipe material.
∫ Install one or more water hammer arrestors upstream of
fast closing valves
∫ Install soft closing lever taps
∫ If taps or control valves are not at the end of the line,
ensure that the outlet pipe is one size larger to eliminate
reverse water hammer.
TM
John Fennell. CEO, International Copper Association
Australia.
COPPER CONNECTION
JOHN FENNELL