Pipes banging when using washing machine!

[Fordulike]

Problem: Pipe or pipes in house, bang every time the washing machine valve shuts the water off.
I drained the water system and refilled, but it only cures the problem for a day or two.

Two questions:

1) What's the standard pipe thread size of a modernish house?

2) Do these water hammer arrestor thingies actually work?

http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR12.TRC2.A0.H0.Xwater+hammer.TRS0&_nkw=water+hammer

Hopefully, someone who is actually using one successfully can comment, as I don't want to spend 30 quid, for it not to cure the problem.


http://rover.ebay.com/rover/1/710-53481-19255-0/1?icep_ff3=9&pub=5575076635&toolid=10001&campid=5337452466&customid=water+hammer&icep_uq=water+hammer&icep_sellerId=&icep_ex_kw=&icep_sortBy=12&icep_catId=&icep_minPrice=&icep_maxPrice=&ipn=psmain&icep_vectorid=229508&kwid=902099&mtid=824&kw=lg

 

[flecc]

Some claim stops the noise, but some say quietens, so perhaps not a total cure.

Of course the source of the problem is the house pipework inadequately clamped. If the pipes are firmly clamped they will not be able to move and create the noise. You could well find that an inadequately clamped single pipe run in your house is the source, and that clamping that firmly will cure the problem.

None of your pipes should be able to move when you try to move them, they should be as firm as the walls they are fixed to.
.

 

[Danidl]

Problem: Pipe or pipes in house, bang every time the washing machine valve shuts the water off.
I drained the water system and refilled, but it only cures the problem for a day or two.

Two questions:

1) What's the standard pipe thread size of a modernish house?

2) Do these water hammer arrestor thingies actually work?

http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR12.TRC2.A0.H0.Xwater+hammer.TRS0&_nkw=water+hammer

Hopefully, someone who is actually using one successfully can comment, as I don't want to spend 30 quid, for it not to cure the problem.

1. Usually 13mm or 1\2 inch. If using copper compression fittings you need to use locally sourced piping ,and olives as there are minor differences between national standards and they are not interchangeable. If using PEX or one of the modern plastic aluminium composites there is a smaller range of fittings, but they are more standardised
2. A small expansion tank , fitted close to the washing machine using using a t piece ( 3way fitting) and joined by a piece of flexible tubing, should dampen the transient pressure waves and water hammer

 

[Croxden]

Or close the main stop tap down a bit.

 

[Fordulike]

Or close the main stop tap down a bit.

Tried that, but electric shower throws up a low pressure alarm.

 

[Croxden]

Tried that, but electric shower throws up a low pressure alarm.

Then put an isolation valve in, cheap and not hard to do.
But flecc is right, look to see where it is moving and put a wedge at the back of the pipe to be sure there's nothing more.