Hi,

I want to replace the non-TRV valves on my living room and dining room radiators with TRVs and wondered whether this is practical without draining the system down. These are both downstairs so would be a pain to drain the system to that level. The pipework feeding the radiators is 10mm and I am hoping that as long as I depressurise the system, only a small amount of water would be lost before the residual vacuum cause by the loss would reach equilibrium and prevent further loss. However, I would like to know if this is the case before I crack it open... I don't mind draining the actual radiator as it has a drain tap on it and have done so before for decorating purposes but the pipework is a different story.

If so, is it possible to extend the pipework slightly if required (ie. can I solder wet pipes with yorkshire fittings and blow-lamp?) because I need to replace one of the radiators due to corrosion and the centreline of the inlet and outlet tails is further from the wall than the one I'm removing. This is because this is the hall radiator and I want to upgrade it to a type 22 (currently 700x600mm type 11) because the hall, where the thermostat is located is always colder than the rest of the house and that causes the thermostat to stay on overheating the rest of the house. I'm hoping that having a bigger radiator in the hall will balance things a bit better. I'm actually reducing the height from 700mm to 600mm to allow the radiator covers which my wife ordered to fit so by going to type 22 with its higher output I should get a net gain. It's a kudox radiator from screw fix btw.

Last question - if I am simply replacing a non-TRV valve with a TRV, is it possible (and/or practical) to just retain the existing nut and olive on the 10mm pipe and just apply some jointing compound or tape to get a good seal on reassembly of the TRV or should I be removing the old olive and/or the pipe it was crushed onto? I ask because our living room radiator valve leaks slightly despite tightening it up a couple of times and I'm not sure what to expect when I try to reassemble it.

Thanks for your time.

Cheers,
Craig.

Bit messy if you don't drain. Black water too usually. You're right about the vacuum though, but you will struggle to solder wet pipes. Myself I'd use pushfits. If you can get the carpet back and get under the floor it's easy. Leaks can be sorted with either ptfe around theolive, or a sealing compound like jet blue.

Don't put your finger over the pipe to stop flow if it has a cut on it

Hi,

The water is fairly clean having been flushed not so long ago and with plenty of corrosion inhibitor. I drained the living room and dining room radiators about 2 weeks ago for decorating and it was clear water with just a trace of black particles at the end when I actually removed the radiators.

The pipes come through the walls in our case and there is some slack for minor adjustment but not the 30mm or so that I'll need to connect to the type 22 radiator. Yes maybe push fits would work but I've had mixed success with those in the past.

The jointing compound I've got is Boss Green with hemp which I think is suitable for drinking water pipe use as well. Not sure about jet blue.

Actually that reminds me of a different question - are TRVs any use when inside the bottom of a radiator cover/cabinet? I'm thinking they might not work quite the same but these rad covers have a big slot at the top and plenty of space at the bottom to draw in ambient air so might still be okay. If there is no point in having a TRV inside a rad cover then I can save myself the hassle...

Thanks

quote:

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Originally posted by dave_424
Don't put your finger over the pipe to stop flow if it has a cut on it

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If you intend to do it here are a few tips. Turn off every radiator to cut down the flow rate, turn off the boiler and isolate with the valves underneath. If you are lucky and prepared to go, it can cause a vacuum so when you open the system minimal water loss could occur, You will not be able to solder wet pipes. However once its drained out as long as the water level is a good 50mm below the join, on 10mm pipe it should be OK. Fit the new rad before altering the pipes. A twist of PTFE will help if you use old olives and can be better then paste if the union is wet. Good luck with it, I do it nearly every day, some times its easy some times the old glugg of water beats me. Push fit is great if all is square and clean

presume combi boiler? if you only disconnect one valve at a time after dropping the pressure you will only lose mimimal water, you may be lucky and have the same threads on the pipe but probably not.
you will not solder pipe with water in use compression or push fit.
and do not touch the isolation valves under the boiler chances are they will leak and cost a fortune to replace sometimes.
cannot stress enough only open one pipe at a time to maintain vacuum, if you have open bleed point etc anywhere and you open a pipe air in water out you get wet.
and trv wont work inside a cabinet but you do get trvs with remote heads for this purpose

I have found pushfit extremely reliable over the years. There are copper pushfits that look rather tidier than the white/grey type Theanswer is to get a good cut with a proper pipecutter and make sure they go in far enough....

quote:

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Originally posted by craig1410

quote:

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Originally posted by dave_424
Don't put your finger over the pipe to stop flow if it has a cut on it

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I take it the corrosion inhibitor is a bit "nippy" is it? Thanks - will bear that in mind. I know it stinks but haven't got it in any cuts as yet. Unlike cellulose thinners - I've had that in cuts before and it's bloody painful!

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Craig -
I find that whenever I try shortcuts it takes longer than if I did it properly. Drain the system down
You will probably find it impossible to get the old olives off the pipe as they will be crushed onto it.

Hi guys, some contrasting advice it seems, but all very much appreciated.

I'll give it a bit more thought before deciding how to proceed. Maybe I should wait until the weather is a bit warmer before starting so I don't end up with a cold house if I get myself in a guddle...

If I do decide to drain the system down then I might as well fit TRVs everywhere (except the hall as it's the bypass radiator). Is it worthwhile fitting TRVs to literally all radiators (eg. small WC, utility room, upstairs hallway) or is it only worthwhile in the larger rooms like dining room, kitchen, living room? I've already got them in all 5 bedrooms upstairs but nowhere else. House was built in 2000 so building regs only mandated them in bedrooms at the time.

Thanks again.
Craig.

Surely it would be much less messy to move the room stat to a much more sensible place ! !

No risk of water damage, anywhere !

No temperature drop when you open the outside door !

No cost of a new radiator !

Put the room stat in the room you live in, the living room ???

quote:

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Originally posted by slingshot2000
Surely it would be much less messy to move the room stat to a much more sensible place ! !

No risk of water damage, anywhere !

No temperature drop when you open the outside door !

No cost of a new radiator !

Put the room stat in the room you live in, the living room ???

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