Changing Radiator Valves on an Unvented System

[topgazza]

Found a few posts on this but with some contradictory advice so thought I'd start from scratch.

I am replacing a bathroom radiator with a towel rail and need to replace the valves as well to straight and not angled. When I had my en suite refurbished the builder employed a plumber who replaced the radiator and valves. I didn't perch on his shoulder but he didn't drain the system to replace the rad and valves. But he did turn the stop cock off which I know removes all the pressure from the unvented system. Does this mean that you can remove and replace the valves, one at a time, without water gushing out ?

 

[Whitespirit66]

You can change rad valves without draining by doing one at a time, but it's not the unvented cyl you need to relieve pressure from. The radiator/cyl coil circuit needs the pressure relieving from, not the water stored in the cyl itself.

Turn off hw and ch and vent a rad bleed valve to drop system pressure (see guage) down to zero. Close both rad valves on bathroom rad and crack open the joint between one valve and tail that screws into rad. Open rad's bleed valve and drain out water. Carefully open one valve to check system holding. If nothing/little comes out, change that valve, close it then do same with other valve. Obviously you can't solder like this, but if just changing valve - should be OK.

If replacing rad with towel warmer, make sure it's output is sufficient for bathroom as some are pitiful. Check BTU/Kw requirements on an online rad sizing calculator.

 

[topgazza]

I was kind of hoping thats what someone would say and that was my thought process as well

Baby steps along the way...

And I agree about towel rails. The rad I'm replacing is the one that is always on, if I understand it right. As its the heat expansion radiator for the system... if that makes sense.

But yes towel rads need careful selection. I've found the right one that suits but I am still deciding about just going for a nice looking designer rad the same size as currently installed....

Thanks for your advice