If you have a triple valve by your hot water cylinder, (it looks like a plastic box with a single wire attached to it and connected to a joint of three pipes) it should have a small lever that points at CH or HW. Set your system up so the Heating is on but the hot water is off, and check this lever has moved by itself to the CH indicator. If it has not, this valve has probably developed a fault and should be replaced. £50 to £60 sould normally buy a new one.
Rupert, May 2010
