Radiator TRV dripping slightly when off - blank it off somehow??

[nia573]

This is my first question here so please bear with me!!
Ive got some decorating to do in my house which will involve removing some of the radiators (has a TRV & Lockshield valve fitted)

In the past when Ive done this, even though the TRV was rotated to the off position fully water was still dripping slightly from it.(system is 20+ years old so I reckon the TRV is past its best) The lockshield valve end was fine & there were no leaks there

Since Ill need to keep the heating on for the rest of the house, so turning the boiler off isnt an option, would it be possible to blank the male threaded end of the TRV that normally screws into the rad? Any ideas of the thread fitting size to ask for please?

Im thinking that this may be the easiest option for now since to replace the TRV completely would mean a complete drain down?

Thanks for any ideas! Im gradually learning about my house plumbing but have lots to learn & I dont want any disasterous floods!

 

[Rickster123]

Depends on the TRV tail type. Most likely to be 1/2" brass cap required.

 

[WHPES]

Yes, a blanking cap from a plumbers merchants. Some valves, even new ones, do pass slightly. No need to replace.

Old syle valves take 3/4" blaking cap

Remember to top up with inhibitor when you fill the radiators again.

 

[PlumbBobBob]

i agree 1/2 or 3/4 brass cap will do to to cap off your trv just get one of each if you're unsure

 

[GQuigley67]

1/2 3/4 brass cap with a rubber washer, because the TRV is thermostatically controlled it will never really shut off completely, if your have the heating on it will weep.

 

[nysk2008]

could you not drain down central heating, remove trv, cap your 15mm feed or whatever it is feeding your rads and refill? I know its a big more time consuming but if your worried about valves letting by etc this could be an option aswell

 

[nia573]

Thats great thanks for the replies & advice - I think it is 1/2" so I now know what to get

The pipe to the TRV is 10mm so is it possible to get a fitting to blank this off if the TRVC is removed completely?

I need to replace the TRV Im sure in the bedroom as the rad is either cold when the TRV is fully closed, or scorching hot even if the TRV is set at the bottom of the dial (theres no difference whether at the bottom or top of the range on the dial) - does this sound like a knackered TRV?

Thanks!
Mike

 

[royston]

Yes you can get a 10mm compression blank, wrap a bit of ptfe around the olive on the pipe, split the new cap end , place cap on pipe and screw existing nut up onto it.