Another water hammer question

[ptarmigan]

Have read all the other posts on this problem and before i try some mods would like to see what others think,the washing machine solenoid is the start of the noise and so far have fitted a Mini Rester to the m/c and it has lessened the noise but that is with the water pressure at 1 1/2-2bar with a prv and the main problem arises when someone is using the elecric shower and the mains water is drawn off the temp rockets before the stat can adjust.
The cold feed to m/c comes down the kitchen wall and has a 90% bend then along to a washing m/c fitting with shutoff.it then carries on to the sink via a half turn full bore shutoff valve and then outside tap but that is not fitted at the moment,all pipework is well clipped and i have fitted a new stopcock on the rising main but having done lots of reading on this i am coming to the conclusion that the full bore shutoff is not what it states and coupled with the other bends in pipework close to m/c is acclerating the water when the solenoid shuts off and causing the noise,just wondered if i am thinking to hard or on the right track before i tackle this problem again

 

[buck51]

what is the problem?
water hammer or shower temp?

 

[ptarmigan]

Hammer,if that is resolved i can turn the pressure back up and the shower will be ok.

 

[buck51]

How far is the first pipe clip from w m valve?

if you hold the pipe can you feel it kick and then vibrate when wash machine valve shuts off?

 

[GavThePlumber]

Fit an expansion vessel after the incoming main, about 20 quid for an 8 or 10 liter vessel, pressure it above the precharged amount until it is sorted.

 

[buck51]

Sorry to have to say this but a Plumber should be able to locate the problem and fix it,

 

[GavThePlumber]

What if it is under a grands worth of flooring?

 

[ptarmigan]

How far is the first pipe clip from w m valve
Buck,
About 6-8 inches and yep it does pulse but if the pressure was back up you can see the w/m hose jump when the solenoid closes.

 

[ptarmigan]

Gav,
Have recently decorated upstairs and had the floor up and clipped the mains and its rigid,thought it might do the trick but FAIL.

 

[buck51]

The OP has tried several bodges that have not worked!!!

I am trying to help him locate the problem and then fix it !!!

 

[buck51]

then how far is the next one ?
and how far along the pipe do you have to go untill you can no longer feel it kick?

I am not meaning the vibration but the initial kick as the valve shuts off

one more point are the clips secure?

 

[ptarmigan]

Next clip is about 5/6Ft as the pipe is sleeved in plastic conduit chased into the kitchen wall then about every 18/24 inches,all the feeds coming off to the loft for fe tank/shower etc are clipped with plastic clips screwed into the wall,ref vibration its not doing that as would a bouncing ball valve,just the one thud as the water is closed off by w/m and as for how far along i have not felt for that as you can here it all over the house as it is quite a long run from the rising main stopcock,thinking about it i can see if i can feel it on the stopcock through the access flap when she next does the washing or get my boy to show me how to work it!(i was born in the age of valves not digital,well thats what i tell her)

 

[GavThePlumber]

The OP has tried several bodges that have not worked!!!

I am trying to help him locate the problem and then fix it !!!

You internet hero, we bow down to you, messier.

 

[Madrab]

How high is the normal water pressure? If the mains pressure is relatively high, over 3 bar, then the hammer will be accentuated, as the pressure wave will be greater that returns down the pipework when the machine's valve closes.
You say you have an arrester connected, is that after the isolation valve to the machine with the fill pipe connected to the arrester? Do you have the standard feed pipe to the machine or is it a longer one? Longer feed pipes can sometimes increase water hammer.
Have you tried closing down the isolator to the machine a bit and see if that helps? Keep turning it down and see if it eases. If not and reducing the pressure helps then locating a PRV just before the WM feed and reducing the pressure to the machine may sort it. It will then allow your other PRV to be turned back up

 

[buck51]

The thud as you describe is usually coming from a section of pipe that is not clipped.

if you are sure you cant get anymore clips on it, then I would move the PRV to just before the washing machine were it comes out of the wall and reduce it right down,(if its the adjustable type it sould go down to about 1/2 a bar)

And that should help with the shower problem also,
And try that, if it works then you can raise the pressure bit at a time