noise when running hot water.

Hi.
Just moved in to a house , and when i am drawing water from the hot tap, not straight away , but after a few seconds there is a humming noise , not sure where the noise is coming from but seem to be the area of the hot water cylinder, or the loft.
The system is an indirectect gas fired central heating system.
seem as tho the noise only starts when the cylinder is recieving the cold water to replenish the hot taken, as the noise still goes on once the tap has been turned off. , but what do i know.The pipe going to the hot water cylinder that replenishes it once hot is take seem to be the area at fault.If i move the pipe a bit the noise changes?
is it an airlock, if so how do i clear it, since i thought that running the tap would remove air lock?
thanks steve
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steve wrote:

Sounds like a mild case of water hammer - I had it once, sounded like a didgeridoo in the loft.
There was a thread in here about it a few days ago if you search on google groups. http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm 9dcb24 .0312020759.172871fb%40posting.google.com&rnum=2&prev=/groups%3Fas_q%3Dwater %2520hammer%26safe%3Dimages%26ie%3DUTF-8%26oe%3DUTF-8%26as_ugroup%3Duk.d-i-y %26lr%3D%26hl%3Den
(sorry about the long link)
Basically, you can change the ball valve, or the washer inside it, or fiddle with the isolation valve to vary the pressure.
Bob
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snipped-for-privacy@yahoo.co.uk (steve) wrote:
Hello steve

Stupid idea, because I'm installing one at the moment and it's occupying my mind - but are you sure you haven't inherited a pressure activated water pump?
(Rule out by cutting power to whole house and trying to replicate.)
If not, then prolly water hammer, or unfixed pipes vibrating, or a noisy ball valve. You're simply going to have to go up and look while somebody else plays with the taps.
--
Simon Avery, Dartmoor, UK
uk.d-i-y FAQ: http://www.diyfaq.org.uk /
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