Combi (Baxi) hot water problem...

[jamesdriscoll]

Hello, I wonder if anyone could help me?

My mother has a baxi comination boiler, about 3 years old apparantly. (AM not sure what model it is though). It works fine as supplies hot water, but she says when the hot tap is turned off, there is a knocking sound, not always but quite often.

Is there anything that could cause this? Water hammer possibly? But why on the hot tap only? Any suggestions please?

Thanks for any help offered

James

 

[jamesdriscoll]

could it be a knocking pipe somehwere even?

 

[plumbplumb]

expansion on the hot pipe where it touches something i.e joist.

 

[jamesdriscoll]

yes I was thinking that, but then it's only when hot tap is turned off, not when it's running...