Draining down central heating system All aspects of plumbing questions and answers, help, tips and information

[funsen30]

Hi - I removed a radiator to plaster a wall and tried to use the therm valve to stop the water instead of draining down the system (but it turned out to be faulty). Is it ok to leave the system drained down for an extended period of say 3-4 weeks or is it likely to cause problems? Thanks

[plumbbob]

Although it is not ideal, you can leave a system drained down for without any problems occurring. It is never a good idea to leave a system dry for an extended period, as the steel starts to rust and any silt starts to dry.

Thermostatic valves rarely shut off water entirely as they will only screw down to a frost setting and not to a true off and anyway, you should never rely on them to stay shut with the radiator disconnected. A flood could ensue.

You can get a 1/2" brass cap for a few pence from any plumbers merchant that will fit over the valve and securely close the end off while you do any work.

[chris_on_tour2002]

if you still have the decorators caps for the therm valves that will help to shut them off a bit more, they are always supplied with the valves though they usually get lost or thrown away.

when removing a rad for any extended period i always cap the valves using the caps that plumbbob refers to, even on the standard shut off valves, just in case.