Evening, just had new boiler and Ch pump. 24hrs later noticed pump was constantly pumping despite schedule being off. Only way to stop it was to turn boiler off, opened airing cupboard to notice slight wet patch from a leaking valve near pump. Fitter sent someone out who drained system and sorted the valve, he said the disc or seal had perished? All seemed fine, but same thing is happening again, obviously without the leak. Any ideas? Yes I will be calling them back in the morning.