Water Hammer - Please, Please Help !!!

[gavioli]

Hi,

Advance apologies for this long post, but please read !

We developed an annoying water hammer ( I think our supplier suddenly increased the pressure)

So I fitted a long piece of 22mm in the loft to trap some air to act as a buffer. This worked a treat, taking out all the noise. BUT about 3 weeks it came back, so I drained the tube and it worked again, for another 3 weeks.

Fed up with this short term (i don't want to keep having to drain this tube) I bought some "mini resters" from local plumbers and fitted to washing machine, toliet etc... The one on the washing machine worked and took out the hammer, but none of the others seem to have any effect.

Then for no reason, the washing machine is now causing the hammer again, even with this mini rester on it.

I went back in the loft, redrained the tube and also lengthened it to see if it will stay OK and all was back good again - no hammer.

Now 1 week on, the hammers back and even re-draining the tube it won't go away.

My question is WHY, oh WHY can't i get rid of this water hammer and why when it worked before do these mini resters and my long length of upright pipe in the loft won't work and make it stop, yet it was all working before - no pipework has been changed ! It's as if the water has discovered these and is bypassing them deliberately !!!???

Any suggestions or help please as it's driving me mad!

Thanks.

Nick

 

[joe-90]

Are you sure that all your pipes are fastened securely? Loose fitted pipes are a known cause of water hammer. When the water stops the impetous of the water continues and hammers the pipe into something close by like a wall or joist.


joe

 

[ricarbo]

Tried changing the floatvalve for a different brand?

 

[gavioli]

Hello guys,

Thanks for your replies.

ricarbo - I haven't change the float, but checked all that and it's seating fine.
when the hot water tank fills, this doesn't cause any hammer - only the washing machine, upstairs toilet, upstairs tap (cold) kitchen tap (cold)

joe-90 - I have checked all pipework previously when I had all the floors up and all is fixed 100%

As said, I got it to stop with the tube &/or the mini resters, but why and how could it suddenly start again?

thanks.

 

[Diyisfun]

If you think your water pressure has been increased, why not close your stop cock a little, to get you back as you were.

 

[ricarbo]

Does the washing machine fill in the time specified in the instruction book? If it's filling too fast you need to slow it down - restrictor in hose, as suoolied with washing machine? Partially close washing machine isolating valve? As said before, look for poorly secured pipework.
These items that have the water hammer - are they mains fed or tank fed?
Fit PRV in mains pipe if they're mains fed?

 

[gavioli]

Hello again,

Tried turning the stop cock round a bit - does nothing. You'd have to shut it almost right off for it to stop, then there is no flow.

I don't want to fit a pressure reducer as we have a trevi boost venturi shower that uses mains pressure to boost the hot supply and that works well. if reduce pressure it won't.

I haven't timed the washing machine - may have to check that.

BUT the whole point is, how can this go back to hammer, when I already cured it and nothing has changed since ?
This is what I just can't get my head round.

Yes, all of these are fed by mains (all our cold supplies are from mains, not tank) All i can think is the next step is to fit prv to all the things that cause it - would that work rather than fitting 1 on the main in, so my pressure stays high to the shower, but just reduces it to washing machine, toilet, tap etc..?

 

[ricarbo]

without claiming to be an expert, i should have thought that if you fitted the one prv on the main and adjusted it correctly, you should be able to achieve a flow to the shower as good as before the pressure increased, whilst limiting the excess to the rest. How about getting a pressure guage and actually measuring what the static pressure is and asking your water supplier what it should be?
do your neighbours also have this problem, starting the same time? Maybe this is something for the water authority to fix?