Knocking from cooling hot water tank
 

Hi,

Does anyone have any ideas what would cause the following problem and
have any solution?

About 1.5 hours after the central heating in my house turns of there is
a loud knocking from the hot tank (I think). The knocking starts of
very quietly and slowly spaced, then speeds up gets very loud and then
tails of again. This lasts about 3 or 4 minutes and it very annoying.

Cheers,

Ian

--
Ian Robinson, Belfast, UK - http://www.canicula.com
Soapbox - http://homepage.mac.com/ianrobinson/index.html