Replaced electrical shower, now have water hammer

Mr.Stu

Mr.Stu

Mr.Stu

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Joined
18 Oct 2002
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2,413
Prior to replacing shower, everything was fine for 8 months.

Water hammer occurs when either cold tap is turned off abruptly, washing machine stops, shower stops etc

If I turn the stopcock off, drain all the water out, and slowly refill, the problem seems to go away for a day or so.

Any ideas? I've followed all the easily googled guides for draining and refilling pipes.

Cheers
 
Also, unless I'm going nuts, I swear I can hear the pipes knocking randomly even when the taps/water is not being used.
 
Have you changed the ball valve in the header (?) tank? This solved it for me when I had which funnily enough occurred 6 months after fitting a new shower too.
 
My understanding of plumbing is pretty poor so bare with me.

But isn't the header tank purely to do with the central heating?

This water hammer I have only occurs on mains cold.

Cheers
 
I've recently had this for the past year or so. Usually hear it coming from the bathroom when washing machine starts and stops filling up etc. Didn't know what it was actually called though.

Had water cylinder and header tank removed this year for a combi and it is still doing it so nothing to do with that. I'm thinking it could be to do when I had the water meter put in, maybe it is letting a higher pressure flow to the property. I can't be certain though as I can't remember if it was happening before I got the meter or not.
 
Often, somewhere in the system, there might be an air chamber (usually a length of pipe which is capped off at one end so that it appears to do nothing. There are also purpose made air chambers that might be used) which are intended to eliminate water hammer. If you have one make sure it hasn't filled with water. If you don't then you can either try reducing the water pressure a little (meh) or look at installing an air chamber, a proper hammer damper would be easiest, just install it inline before the offending valve (usually a shower/washing machine....things with solenoids that cause sudden changes).
 
Appreciate the tips but what would explain it happening since a shower replacement, and also the fact that draining the system and refilling slowly seems to cure for 24 hours?

It is not just the washing machine or shower, closing any cold tap in the house triggers it!
 
Water hammer is caused by the momentum of water being suddenly stopped by a closing valve. The longer the run the worse the hammer. Bends can help as can accumulators that smooth the pressure spike. It my have been that you old shower acted like an accumulator or a leaking valve acted like a pressure relief. In industry valve actuators are designed to close the last few percent slowly and relief valves are fitted. In the home a few sharp bends can help changing the direction of the force and acted as a spring inthe pipe run. Accumulators placed near the worst offending devices will help.
 
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