Changing a downstairs RAD VALVE to Thermostat without draining off the whole system.

[keepitreal2025]

Hi all,

I am not a plumber/engineer so appreciate any help.

I am wanting to change a rad valve downstairs on a pressurised combi system. I have watched several videos on the Tube but cant decide which is the best way to do it without doing a complete drain down which is time consuming.

My question is can I do this by shutting off the boiler, isolating the downstairs rad closing off both valves left and right first, releasing the pressure from the bleed valve to a slow trickle and slowly letting the rad drain from the valve nut off the rad to a workable flow and then swap the valve to a thermostat without panic???

I have watched several ways, one being to isolate the rad in question and bleed off, then bleed another rad to drop the pressure?
Also another said to close off all upstairs valves and lock shields to prevent a backflow?
Another said to fully drain off so it's a mixed bag. One didnt even depressurize the system and just did it live but it was gushing out for a couple of seconds.


Any advise will be gratefully appreciated. Once i have done this and confident i will do a few more and replace the old rads and incorporate some inhibitor.

 

[keepitreal2025]

Just to add to the above. I am keen on DIY especially plumbing, about 10 years ago i tried to get on a heating engineers course in Bolton Manchester but due to lack of government funding the centre closed down so i was gutted. Ended up going down the IT route which i regret in some ways as it makes you lazy.

My property which me and my partner own is pretty old so at least 3 rads need to be changed. I thought if i get the hang of the TRV upgrade then i will for sure be able to do that new rad installs. Seen some vids on the Magnolite gadget that catches all the rusty iron debris but i wont go ahead of myself just yet

 

[keepitreal2025]

Thanks for all the help NOT

 

[aveatry]

Things can get missed on the forum.
I would go with all valves off, drain the read in question, release pressure via another rad.
Get fully prepared, can the old olive come off easily or will it stay. But my top tip is to get some puppy training pads to soak up any water they are dead cheap and work better than old towels.

 

[keepitreal2025]

Thanks, I already done the job earlier. Didn't go in blind but still came across minor problems as u can imagine. Lock shield valve caps on all the rads had rusty screws and couldn't take them off but just hoped they shut off by turning fully right. Released the pressure from the bleed valve I was working on and drained about 4 litres of water until the flow settled down to work on. Think this was due to one of the upstairs rads draining off. Removed the old valve, took a bit to get it off the pipe as it was just twisting but managed it. The olive looked v worn and I couldn't get it off to replace so put some jointing compound on and swapped the trv valve. Tightened up, pressurised the system and bled again. Was only one rad needed bleeding upstairs. No leaking so far and I am happy. Took about 1 hour in total. Took my time and reckon I'll do it in 30 mins next time. Ordered some grips from Amazon as spanners are too fiddly to support the valve while tightened the union nut

 

[StephenOak]

The top post in this section is

SHARE YOUR DIY PROJECTS WITH US - >> NO << QUERIES HERE Please !!!!!

There is section for plumbing & central heating where this would have been replied to sooner.

 

[aveatry]

Thanks, I already done the job earlier. Didn't go in blind but still came across minor problems as u can imagine. Lock shield valve caps on all the rads had rusty screws and couldn't take them off but just hoped they shut off by turning fully right. Released the pressure from the bleed valve I was working on and drained about 4 litres of water until the flow settled down to work on. Think this was due to one of the upstairs rads draining off. Removed the old valve, took a bit to get it off the pipe as it was just twisting but managed it. The olive looked v worn and I couldn't get it off to replace so put some jointing compound on and swapped the trv valve. Tightened up, pressurised the system and bled again. Was only one rad needed bleeding upstairs. No leaking so far and I am happy. Took about 1 hour in total. Took my time and reckon I'll do it in 30 mins next time. Ordered some grips from Amazon as spanners are too fiddly to support the valve while tightened the union nut

Whilst you are shopping get yourself an olive puller.

 

[keepitreal2025]

Okay I did have that it mind but where does it end hey lol. I was going to cut it with the junior axe saw but thought I don't want to risk the pipework getting chewed up. I did try pliers but it wasn't having it. My next rad that's needs attention doesn't get hot, just loop warm, both valves open, doesn't need bleeding and the pin under the trv head appears to be ok as in risen above the para pit. It's about 30% heat compared to the others. A massive old single rad, it's about 4 meters long. Not sure if the trv has failed or maybe it's clogged up..

 

[aveatry]

Okay I did have that it mind but where does it end hey lol. I was going to cut it with the junior axe saw but thought I don't want to risk the pipework getting chewed up. I did try pliers but it wasn't having it. My next rad that's needs attention doesn't get hot, just loop warm, both valves open, doesn't need bleeding and the pin under the trv head appears to be ok as in risen above the para pit. It's about 30% heat compared to the others. A massive old single rad, it's about 4 meters long. Not sure if the trv has failed or maybe it's clogged up..

If you had a puller then that new valve would have also had on a brand new olive

 

[keepitreal2025]

Doubt it will leak even if the olive was shafted. I used V2 Jet jointing compound lol. Take heed plumbers