problems with hot water / central heating

[Aridane]

Have gas central heating and hot water, each with separate controls.

However, for some reason, even when the hot water is not switched on, the water is always hot. I think maybe it is coming on automatically when the central heating is on. (and, no, I haven't accidentally left the immersion on).

Anyone any idea as to what this might be or is it simply the case of calling out a gas engineer?

Is it not stored in a hot water cylinder? My hot water is only on a couple of hours a day but we always have hot water available

How long has the water heater been switched off for?

A large, well insulated hot water tank can keep the water hot for a couple of days if used sparingly!

Ah, no - unfortunately it's not as simple as the water being kept hot for a couple of days. The water was piping hot this morning despite not having been on for a couple of days.

SomI ran the water this morning until stone cold. And it stayed cold. But this pm, after having the heating on for a few hours, the water is hot again.

I had the same and also the radiators used to stay on even after turning the heating off. I needed a new valve

Ha, mega - you genius, it was to do with the valve and needing a new one. The British Gas engineer was (mildly) impressed when I said I thought it might be the valve!