Banging pipes

[ck80]

We had a new Worcester boiler fitted. They installed a expansion valve with it ( globe shape object off a pipe under boiler)
Then followed months of banging pipes when washing machine taps are put on.

The boiler fitters did visit . Fitted new valve in toilet, 2 new showers, expansion valve by washing machine and one at stop cock. Also tried to isolate , take off dead legs , clipping pipes, drained pipes.
Weirdly it reduced the bang,but eventually came back as loud as before.
The pipes are loose in the extension garage . However, no pipes banged with old boiler.

The boiler plumber then stopped returning my calls.

A new plumber came in. Replaced bath tap, sink tap. No difference.
He then took the expansion valve off by the boiler. This has massively helped. It was the valve that was causing the banging upstairs.

So now I can just hear bangs when I'm near the washing machine downstairs in the garage.
So my question is, should I call the plumber to remove the expansion valves or a washing machine engineer to look at the machine itself. ( I think the machine works fine, but hear a clunk or bang when takes in water)
The new plumber does not know why the expansion valve caused the bang.

I have spent thousands on a boiler. Now nearing 1000 to fix the banging. Just trying save money.

Any ideas would be so helpful
Thanks

 

[opps]

I am not a plumber.

Has he suggested fitting a water hammer arrestor?

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They are designed to absorb the kinetic energy when turning off a tap.

 

[ck80]

I think that's why they fitted 3 expansion valves. Do they do the same thing??

I will ask the plumber what he thinks about the arrestor too. Thanks so much.
Don't know if it makes a difference, but the bang is when water turns on. Not off

 

[opps]

I think that's why they fitted 3 expansion valves. Do they do the same thing??

I will ask the plumber what he thinks about the arrestor too. Thanks so much.
Don't know if it makes a difference, but the bang is when water turns on. Not off

Again, I am not a plumber...

I have only experienced water hammer when a tap or valve is closed, not when it is opened.

I can only guess that opening a tap is possibly causing a pipe to hit another pipe or joist/etc. If that is the case, no I don't think a water arrestor will help.

I suspect that you need one of the plumbers to comment, eg @Madrab . Sorry, I am out of my depth here.

 

[Harry Bloomfield]

I have only experienced water hammer when a tap or valve is closed, not when it is opened.

I can only guess that opening a tap is possibly causing a pipe to hit another pipe or joist/etc. If that is the case, no I don't think a water arrestor will help.

I agree! The hammer when a tap closes, is due to the inertia of the weight of the flowing water.