Water Hammer


Postby halfpennyacre56 » Thu May 06, 2010 4:15 pm

I have had a new kitchen fitted with the new ceramic 90 degree taps. The new taps, dish washer and washing machine were causing water hammer so I have installed a water hammer arrestor under the sink which is close to all three units This has stopped the water hammer from the taps and dish washer but not the washing machine. Please advise how I can correct this.
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Postby plumbbob » Fri May 07, 2010 10:27 pm

You should really find out what is causing the water hammer. Although this can be tricky, it really is advisable to make an effort to correct the fault.

The favourite cause is where a length of pipe has been capped off resulting in air being trapped when the supply is turned back on. This can be a health hazard as well as a nuisance.
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Postby halfpennyacre56 » Fri May 14, 2010 7:53 am

I was under the impression that water hammer arrestors contained a chamber separated by a flexible diaphram the top side containing air. The water pressure spike which arrises from shutting off the water to taps and washing machines etc very quickly, reaches the arrestor and the air in the top absorbes the water pressure spike stopping the system from banging.
I appreciate what you said about finding the actual cause of the banging but this would involve a great deal of expense and work chasing pipework under floor boards etc.
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Postby plumbbob » Sat May 15, 2010 7:54 pm

halfpennyacre56 wrote:I was under the impression that water hammer arrestors contained a chamber separated by a flexible diaphram the top side containing air. The water pressure spike which arrises from shutting off the water to taps and washing machines etc very quickly, reaches the arrestor and the air in the top absorbes the water pressure spike stopping the system from banging.


You are correct in your assumption. However, if the hammer is being produced in a different leg of the pipework, it is possible the arrestor won't work.

halfpennyacre56 wrote:I appreciate what you said about finding the actual cause of the banging but this would involve a great deal of expense and work chasing pipework under floor boards etc.


Well, that's up to you, but I wouldn't leave it!
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Postby dripbusters-ltd » Thu May 20, 2010 10:31 am

15mm copper pipework in homes should be clipped every 1.2m on horizontal runs and 1.8m on vertical runs (these are minimum values).

I suspect the problem here is that this has not been done in your house. Given that you say that this has only become a problem since your new kitchen has been put in, I would suggest that the problem is not the new tap/dishwasher/washing machine but a lack of clips on the new pipe runs in the kitchen. Can you pull out the dishwasher and washing machine to check how many clips are holding the pipes to the wall?

Often with water hammer the shaking of the pipes in the house gives a clue to where the problem is. We had a similar problem in the kitchen of our house - every time the tap was closed off you could hear a banging in the ceiling void of the kitchen. We did our bathroom recently and on lifting the floorboards it became obvious that the person who put the last one in hadn't heard of pipe clips! A few clips and the problem was sorted.
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Postby TheDoctor4 » Thu Jul 22, 2010 8:52 pm

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