steve wrote:
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

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=e...readm=ab9dcb24
..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