Drain Or Don't Drain

[Bob906]

I want to replace the bleed valve on a radiator which is seized up with paint etc.; will turning the main rad valves off be enough to change the bleed valve or will I have to drain the rad as well.

Thank you all in advance.

[Mosaic]

I think you will need to shut off both valves to the rad and let it empty.
Hattie's advice is usually easy to follow:
http://www.stopcocks.co.uk/category/how-to/ see installing a radiator, part way down page

[The Builder]

It depends, Bob. If it's over good carpet, then I'd suggest finding the drain off point for the system and letting some drain. The trouble is, if it's a downstairs rad, then you'd have to drain upstairs completely.

To avoid this, you could simply crack open one end of the rad and collect a little water, but it could be messy. (Remember to turn off the rad valves first.)

If it's over vinyl or something moppable, then most plumbers would do it "live". They would remove the old and bung in the new valve sharpish......... before too much came out.

[heathfield]

Shutting off both valves will prevent any water flow into or out of the radiator. But any water above the level of the bleed screw will dribble out when the screw is removed, A baking tray and a couple of towels will come in handy.

[malagabob]

If the inlet valve is wheel type it should isolate rad in conjunction with return valve. Thermostatic flow valves are prone to passing even in the fully shut position.
You will need a air vent plug tool to remove plug. Or adjustable spanner if plug has flats.
Replace with new plug (which has O ring or add PTFE tape to threads) and bleed nipple.