4 hours ago Jo asked ... How to engage clutch on old sewing machine to engage needle?    |    Jacky asked ... Miele Vacuum cleaner?    |    Ben asked ... Toyota Yaris French or Japanese?    |    Andy asked ... How can I mend my MacAlistair 450w hedge trimmer?    |    Felix asked ... Hitachi vt-m70em?    |    Click here to ask your question

valliant tubomax gb 820 noise?

boiler is making high pitch noise when central heating on. The noise stops as long as the hot water tap is on.Noise goes off when the boiler is switched off and also when central heating is off.
What is the proble? How to mend it?
S Chatterjee, August 2009