Hi all I've had a problem with only having warm water coming out of a bathroom basin hot tap, being fed by a combi gas boiler.
We had an engineer out thinking the boiler was at fault, but when he turned the cold water feed to the boiler off, water was still coming out of the hot tap.
He told me that there must be a cross in the domestic pipework somewhere as the water should have stopped flowing when the boiler was isolated.
I'd done most of my own pipework in the house and immediately thought I was in that street again and I don't mean quality street.
But I got to thinking that the water works used to be fine, it was something which had come on over time.
The shower was also running cool and then sometimes go cold.
There is an isolating valve in both the hot and cold supplies to the shower I turned them both off, Bingo the water stop flowing from the hot tap when the boiler was isolated from the mains.
Clearly there must be something wrong with shower mixer or its thermostat.
I have now put a double check valve into both the pipes to the shower and now when the boiler is isolated the water does stop flowing from the basin hot tap.
Two questions:
Can anyone tell is it possible for the cold water to get into the hot water side of the system when shower is not being used  
The water from the shower is still not as hot as it should be, has anyone got any ideas on the likely cause

Hello the scruff.

Thank you for your reply, no I've not checked the filters but I will do.
Can you tell me how I go about re-setting the hot valve please?

I don't usually run it on too high flow as I'm not into power showers if know what I mean, just wondered if the thermostat maybe up the creak, although the whole unit is only about a couple of years old.

I've had the shower from new and there never was a manual with it other than fitting instructions plus how to polish it,very useful, so I guess I'll have to surf the net and maybe find something about re-setting the valve on there.

Thanks for your help I'll have a look at that site, well that is when I get back to my computer, I'll be off it for fews days but I will certainly let you know how I get on.

Signing off now got a long drive tomorrow.

Cheers

Clive

Surprised the engineer who came to look at the boiler didn't point you towards the shower mixer as a likely cause. Makes you wonder how good he was, although perhaps he knew that was a likely cause and just didn't want the job of fixing it.