Hi all.

We have a gas combi boiler with hot water running to a bath mixer tap / shower unit. The usual type, simply fed by one hot & one cold pipe (I think).

HOWEVER, if you run the hot tap only with the selector turned so the shower is on, the water is boiling hot. But if you then flick the selector so the tap is running, the water goes luke-warm or sometimes really quite cool.

I'm completely confused by it!

Let me know if you have any theories or if there's anything I could try.

Cheers.