Fitting new valves.

[kev kelleher]

I need to fit a new trv and a lockshield valve is it possible to partly drain the central heating system?, the radiator in question is upstairs on a sealed system combi boiler, if it is possible how would i do this, cheers.

 

[PrenticeBoyofDerry]

It is possible, but you have to drain the radiator down that new valves are being connected to and pipework above the radiator. Shut all valves on rads above the tails you are working on, then those rads will not drain down. That is providing the exiting valves do close. Remember to turn boiler off, when doing the work.

 

[terryplumb]

look for a drain cock on any downstairs radiator ,some are integral to the radiator valve ,where you can attatch a hose pipe. make sure all upstairs radiator trv ( or wheel head ) valves are open. do not touch any lockshields. after opening the drain cock water will start to run through the hose .you then go to each upstairs rad and using the bleed valve ( at the top of each rad where you usually vent / bleed air from ) open to allow air INTO the rad.then close the bleed valve and do the same to each upstairs rad.when the water stops running out the hose ,you can then work on the rad that you want to change valves on.

 

[Mottie]

When I changed a leaking valve on mine (sealed system), I opened the drain valve and just released the pressure from the system until it slowed to a dribble then I quickly changed the valve. Being sealed, no air got into the system so hardly any water drained out (well, a little bit but I had a towel handy). Job done, bled and repressurised system. I couldn't had done that when it was a vented system, I would have had the pressure of the entire system trying to force its way out when I whipped the valve off.