water hammer

[stgiles]

hi,
i have a problem with water hammer in a direct cold supply. it started a couple of weeks ago and it happens when any cold water appliance turns off. i have'nt carried out any recent work so i know that the pipework has'nt fallen causing any airlocks. all i can think of is that the flow velocity has been increased somehow. what do you think?

 

[migoplumber]

water hammer is nasty and complicated.
its normally related to a single washer failing in a tap/cistern but you say its effecting everything?
is there any appliance that makes it worse.
has ther been any work done in the street lately
are you mains or gravity fed

worst case scenario with no obvious solution, install an expansion vessel in your system

shaun

 

[stgiles]

hi,
it comes straight off the mains and as far as i am aware there has been no work outside. if it is a trapped air problem do you think that draining down the system and refilling would cure it?. i should'nt have to fit a expansion vessel on the system should i?. maybe i should contact the water board and see if they have done anything.

 

[flat pack]

what cold water appliance turns off.

 

[bobpape]

Allthough water hammer is effected by flow and pressure it is not caused by either,



In fact water hammer is caused by the frequency pulses inherent in pumped water acting (resonating)on the clapper in a stop/ball cock or tap



Years ago the problem was solved in most instances by teeing off into the cock (as opposed to using an elbow) and fitting a 6 or 8 inch length of capped off pipe which because of the trapped air
acted like an accumulator that damped out the pulses. I have to tell you that it does not work every time,
but in some circumstances it is worth a try,



If it is occurring in a tap try wedging the clapper (a strand of wire from a wire brush works a treat) if that stops it then the tap is at fault, you either have to inhibit the
propensity for the clapper to resonate, this can be achieved by raising a burr on the clapper spindle, or replace the whole tap,


If it is occuring at a ball cock then change it for a brass equilibrium ball valve or even
Torbec sometimes works,

 

[dontknowitall]

If the water pressure is high, I'd test it and if it's over 5 bar, it will probably be sensible to fit a water pressure reducer valve (around £40) to bring the pressure down to 3 bar.

(I went to a house recently where it was 8 bar and broke the shower. After fitting one of these valves it sorted the shower out and made all the basins and loos function normally too.)