Combi boiler water runs hot then cold

[davidctid]

Hi

I have a Worcester combi boiler and recently the water from the hot water tap has started as hot but then run cold and back to hot. The situation has now started to get worse and in order to get hot water I have to open the hot water tap only partially.

Has anyone go a suggestion as to what might be causing the problem before I use the Homecare agreement I have with British Gas. I have heard some horror stories of BG overcharging for the wrong cause and want to be forearmed with a little information before I telephone them

Many thanks

[htg engineer]

Probably a split or stretched diaphragm, do you find it worse when there's more demand on the cold mains (first thing in a morning or tea time).

[davidctid]

Thanks htg.

There doesn't seem to be a specific pattern as to when the symptoms are worse. Is it difficult to identify / replace the diaphragm?

Regards