Why does boiler make a noise when using hot water?

Tim Gill, December 2007

if it's a high pitched noise the primary heat exchanger has a buildup of debris and needs to be chemicaly cleaned or your inlet gas pressure is too high.

nik, January 2009

Sounds like the plate heat exchanger has had it. Also check your pressure should be 1-1.5 bar that might shush it up (but it probably wont hold). I had one of these and it sounded like a jet engine. Needless to say it's now down at the scrap yard these things are renowned for breakdowns.

mrplumb, January 2008