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.
is it an airlock, if so how do i clear it, since i thought that running the tap would remove air lock?
thanks steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
steve wrote:

Post to this newsgroup: uk.d-i-y very helpful blokes...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hi:
Had problem similar to yours....mine turned out to be "water Hammer"
you might try this site
http://home.comcast.net/~entreken/fixit.htm
go to page two and scroll down to Sump Pumps and Water Hammer
HTH

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.