water hammer

[Stephen]

Hello,

Whenever we turned on our cold water taps, the pipes made a knocking noise, so I fitted a PRV and reduced the mains from 4 bar down to 3 bar and this has cured the knocking.

However, whilst it has solved one problem it has created another: our toilets have torbeck valves in them and now when the cistern fills up, there is a bang as the valve switches off.

Is there a way to cure this hammer, so our pipes can be peaceful at last?

Thanks, Stephen.

[Lobster]

Do you have individual isolation valves on the feed pipes to the toilet cisterns? If so have you tried partly closing these - it can sometimes help?

David

[dmc]

Had exactly the same problem, and largely cured it by shutting the valves on the loo down. Problem was it took ages to refill then.

When we had the boiler replaced the plumber noticed the problem and fixed it while he had things drained down without me asking (apparantly he used the loo and realised it took forever to fill :))

We now have something very similar to

to the incoming mains. Completely cured the problem.

YMMV,

Darren

[Dave Osborne]

I found this publication, which you might be interested in:

[John]

quality washing machine hoses can cause the problem if their walls have become elastic. Turning off a tap causes a pressure wave to make it swell and it then recoils.

Good article - I especially like the fact it explains that a partly closed service valve is not a pressure reducing device.

[meow2222]

> fitted to the incoming mains. Completely cured the problem.

A simpler option is an upward pointing leg of pipework just a few inches long. It gradually fills with air from the water, then acting to absorb shocks to some degree

[Ian_m]

I once changed the incoming mains water from copper pipe to plastic (Hep2O) and that cured the water hammer as a side effect.

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[Stephen]

It isn't the washing machine because even with that disconnected, I still get the noise. The noise only occur when the toilet torbeck valve closes; opening and closing taps does not make any noise.