I'm trying to troubleshoot a problem before calling a plumber/gas engineer: when hot water is turned on the radiators become hot. It's a conventional boiler with a hot water tank.
Is there an easy way to find out whether or not the problem is due to a faulty valve or a more serious and costly to fix reverse circulation plumbing problem?
I figure that leaving the problem as it is is at best going to be burning money - hot water running uselessly around the radiator pipework.