Problem with water hammer and PRV

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Derbyshire
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I live in an area which has very high water pressure, although for the past ten years this has not caused any obvious problems. The cold water supply to the house comes in directly from the mains i.e. no tank in the loft.

A few weeks ago I had a washer changed in a cold water tap in the bathroom (which is upstairs). I then started experiencing "water hammer" effects from that tap whenever it was turned on or off. The plumber reckoned it might have been the new washer turning the flow on/off more abruptly than had previously been the case and this, combined with the high water pressure, might be causing the banging noise. Just to reiterate - no other tap or appliance in the house suffers from this problem. Does it sound likely that something as simple as a new washer could cause water hammer or similar effects?

In order to try to solve the problem I this week had a Comap Safeguard PRV fitted just after the stopcock (I had previously been advised by the Corgi engineer that this might be a good idea anyway because of the high pressure).

Two things have become apparent;

1) The banging associated with the tap has reduced, but not gone away.

2) In operation the PRV is extremely noisy - producing a high-pitched "wooshing" sound whenever water is drawn from the system.

So, 100+ quid later on, I'm not sure if I'm any better off as the banging is still there (albeit reduced) and I now have this very intrusive noise to live with. The PRV and stopcock are located within a small cavity in the wall which is accessed by a wooden door. I have thought of lining this cavity with soundproofing material in order to reduce the noise levels, although I realise that some noise will still be transmitted through the pipework.

A couple of questions, then...

1) Is it likely that simply changing a washer could bring on "water hammer"?

2) Is it normal for PRVs to be noisy in operation?

3) If the answer to 2) is "yes", is there anything that can be done about it?

What started out as a simple "few quid" job seems to be taking on nightmarish proportions and I am presently thinking of asking the plumber to remove the PRV as overall I don't think there's much net benefit in having it, and the noise is very intrusive. Any opinions or observations that anyone can offer would be greatly appreciated as I really don't know what to do next.

Thanks in advance...
 
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lets start with what you call water hammer, do you mean one loud clunk from the pipework, or a loud buzzing noise/vibration.
the fix is usualy the same, refix / reclip the pipe,

as regards the noise from prv,dont think I can help as I have never come across a noisy one
 
lets start with what you call water hammer, do you mean one loud clunk from the pipework, or a loud buzzing noise/vibration.
the fix is usualy the same, refix / reclip the pipe,

as regards the noise from prv,dont think I can help as I have never come across a noisy one

Apologies if I've used the wrong terminology... what I meant was a single "clunk" on opening or closing the tap. No apparent noise when the water is running or when the tap is off.

I should also have added that the PRV is presently set to 3 bar.
 
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what cylinder do you have?

If its a ariston or the like is the expansion tank connected by a metallic hose
which way up is it??
We have had many problems like yours , most are overcome by piping the expansion valve in 22mm copper instead.
yes prv make a whooshing noise thats wot they do.
Say your main is 8bar that prv is causing a massive resistance to the water so that its say 5-6 bar directly after and then the unvented prv will in turn reduce it to 3.5bar.
Water baord recently advised me to reduce it 2 stage like that, if you comap is 3.5 bar fixed maybe the issue what is the static main during the day pressure? should say on the unvented banchmark cert.
 
I had a very similar problem recently. Customer had a loud bang every time a tap was turned off.

When I removed the head from the stop cock, the rubber washer was missing from inside. This caused the brass jumper to move, and bang against its seat when a tap was closed.

Maybe, just maybe, when your plumber turned off the stop cock to change your tap washer, the washer in the stop cock was on its way out. Perhaps using the stop cock made the washer disintergrate.
 
I had a very similar problem recently. Customer had a loud bang every time a tap was turned off.

When I removed the head from the stop cock, the rubber washer was missing from inside. This caused the brass jumper to move, and bang against its seat when a tap was closed.

Maybe, just maybe, when your plumber turned off the stop cock to change your tap washer, the washer in the stop cock was on its way out. Perhaps using the stop cock made the washer disintergrate.

But it's only happening with one tap, located the furthest away fom the stopcock...?

Had a word with the water company today and they reckon that pressure in my area varies between 6 and 8 bar, so the various comments I've had about high pressure would seem to be valid.

Thanks for all the suggestions made on here. It looks like;

PRV noise is inevitable (though I'll talk to the plumber about this tomorrow)

Could be worth checking that the pipes are properly secured. Thinking about it, the noise does seem to be coming from somehwere under the bathroom floor, so this idea might have legs.

Definitely not a cylinder/ballcock problem as I don't have one!

Thanks again for the help...
 

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