I've switched the heating off and left the water on but it looks like the pump is still going.
Thanks guys for the replies, you've been a big help. Looks like I need to get a new valve sorted. :) Best phone a plumber tomorrow...or my Dad :wink:
Any ideas? Heating is on, red hot, but though there's water in the tank it's not getting hot. The pipes are hot up to the what looks like a valve (duoval). Help needed please :?