Replacing radiator without draining down?

pledgeX · Apr 28, 2019

I've removed a radiator from the wall. The trv and lockshield are still attached to the pipes but turned off. Heating is still on and other rads are still working.

I've got a new radiator, trv and lockshield to fit.

I've read some guides on how to replace the radiator, but they all mention draining the system down, but I'm struggling to work out why.

If I shut off water supply to the boiler, and turn the boiler off, why can't I just take the trv and lockshield off and replace them? The rad is on the top floor, but has flexi pipes so I can easily catch any bits of water still in the pipes when I move them around.

Or would all the other rads on the top floor drain out into the pipes I've just opened? What about if I shut the trvs and lockshields on all of them?

Ive got a combi boiler and the pipes for each rad run directly back to the boiler.

Thanks for any help (as you may have guessed I'm new to this!)

SimonG · Apr 28, 2019

Open vented or sealed system?

Burger · Apr 28, 2019

SimonG said:
Open vented or sealed system?

Sealed - he’s got a combi

Burger · Apr 28, 2019

You should be able to isolate the flow and return under the boiler, after draining and removing the radiator, catching any water you can then open up trv side into a bucket and same for lockshield side (count the number of turns - for balancing). Fit new rad and valves, open them up (remembering to count the lockshield side). Open flow and return under the boiler, re-pressurise system, bleed rad and check for leaks.

Aire · Apr 28, 2019

CBW1982 said:
Sealed - he’s got a combi

You never seen an open vented combi?

Burger · Apr 28, 2019

Craig Watson said:
You never seen an open vented combi?

I guess not - I do lack a lot of knowledge due to where I work

Rob Foster · Apr 28, 2019

pledgeX said:
I've removed a radiator from the wall. The trv and lockshield are still attached to the pipes but turned off. Heating is still on and other rads are still working.

I've got a new radiator, trv and lockshield to fit.

I've read some guides on how to replace the radiator, but they all mention draining the system down, but I'm struggling to work out why.

If I shut off water supply to the boiler, and turn the boiler off, why can't I just take the trv and lockshield off and replace them? The rad is on the top floor, but has flexi pipes so I can easily catch any bits of water still in the pipes when I move them around.

Or would all the other rads on the top floor drain out into the pipes I've just opened? What about if I shut the trvs and lockshields on all of them?

Ive got a combi boiler and the pipes for each rad run directly back to the boiler.

Thanks for any help (as you may have guessed I'm new to this!)

So far so good, do not remove the trv or the the locksheild. just replace the rad and re connect ..maybe using extension diy stuff, then open the valves and re pressurise the system ..to 1.5 bar on the boiler
...when off and cold. its not a good idea especially in winter to trust a trv closed ..because they are a bit thick..and when it gets cold will just open to,heat the room even if there is no rad to feed,...so with no rad to,fill the trv will just dump,the contents of your heating system all over the floor and below
centralheatking

Rakesh · Apr 28, 2019

I usually switch all radiator valves off from the trv’s or any valves that aren’t lock-shields
If accessible, isolate flow and return at the combi boiler
Than drain and change each valve independently. Don’t drain both valves together.
Best way without drain down.
If it’s upstairs rads, then only isolate rads at the same level or above.
Isolating the boiler conserves water in the expansion vessel as long as there isn’t one fitted externally.
External ones are only usually fitted if the internal ones fail and are inaccessible.

Harvest Fields · Apr 28, 2019

Try it and find out

Harvest Fields · Apr 28, 2019

Rob Foster said:
So far so good, do not remove the trv or the the locksheild. just replace the rad and re connect ..maybe using extension diy stuff, then open the valves and re pressurise the system ..to 1.5 bar on the boiler
...when off and cold. its not a good idea especially in winter to trust a trv closed ..because they are a bit thick..and when it gets cold will just open to,heat the room even if there is no rad to feed,...so with no rad to,fill the trv will just dump,the contents of your heating system all over the floor and below
centralheatking

If changing rad. Always change valves.

SimonG · Apr 28, 2019

Dump and snatch.

SimonG · Apr 28, 2019

Or just cut old valves off, new insert and new valve over a bucket.

SimonG · Apr 28, 2019

Oh and hope any auto air vents are closed.

MC78 · Apr 28, 2019

pledgeX said:
I've removed a radiator from the wall. The trv and lockshield are still attached to the pipes but turned off. Heating is still on and other rads are still working.

I've got a new radiator, trv and lockshield to fit.

I've read some guides on how to replace the radiator, but they all mention draining the system down, but I'm struggling to work out why.

If I shut off water supply to the boiler, and turn the boiler off, why can't I just take the trv and lockshield off and replace them? The rad is on the top floor, but has flexi pipes so I can easily catch any bits of water still in the pipes when I move them around.

Or would all the other rads on the top floor drain out into the pipes I've just opened? What about if I shut the trvs and lockshields on all of them?

Ive got a combi boiler and the pipes for each rad run directly back to the boiler.

Thanks for any help (as you may have guessed I'm new to this!)

Your combi boiler runs from the mains pressure water pipe leading into your property, therefore your system will be pressurized, the tvr and lockshield are the only two components when in locked or off position stopping that pressurized water from spraying out of the pipe work, if you was only going to attach a new radiator to exiting pipe work it is ok to change rad without draining system, but if you are wanting to change the whole of the lockshield and tvr components then draining the system is advised.

Ben-gee · Apr 28, 2019

Do ‘em one at a time and it’ll hold, as long as no aav open, I do it all the time - no need to drain down.

MC78 · Apr 28, 2019

Ben-gee said:
Do ‘em one at a time and it’ll hold, as long as no aav open, I do it all the time - no need to drain down.

So if you detach the lockshield off the pipe which is pressurized with water, you will not get wet?

Harvest Fields · Apr 28, 2019

MC78 said:
So if you detach the lockshield off the pipe which is pressurized with water, you will not get wet?

Once again. Try it and find out. But I wouldn’t.

MC78 · Apr 28, 2019

Harvest Fields said:
Once again. Try it and find out. But I wouldn’t.

So I have been disagreed for the right advice

Burger · Apr 28, 2019

MC78 said:
So if you detach the lockshield off the pipe which is pressurized with water, you will not get wet?

You relieve the pressure by opening the lockshield after following all other steps I have listed and you wouldn’t get wet. Done it loads of times.

MC78 · Apr 28, 2019

CBW1982 said:
You relieve the pressure by opening the lockshield after following all other steps I have listed and you wouldn’t get wet. Done it loads of times.

Would you not need to isolate all other rads to drain only the one as they are all connected? Now I am confused lol

Burger · Apr 28, 2019

MC78 said:
Would you not need to isolate all other rads to drain only the one as they are all connected? Now I am confused lol

I have never had to, isolate he flow and return under the boiler, should create a vacuum, plus it’s only for vertical pipes

Ben-gee · Apr 28, 2019

Just open valve and catch the water , shouldn’t be much, then you can cut/ solder whatever you want !
I do this on open vented too just put a 22mm speedfit cap on the vent and a carrot in the feed!
Honestly this is pretty basic stuff i thought we all did.

MC78 · Apr 28, 2019

Ben-gee said:
Just open valve and catch the water , shouldn’t be much, then you can cut/ solder whatever you want !
I do this on open vented too just put a 22mm speedfit cap on the vent and a carrot in the feed!
Honestly this is pretty basic stuff i thought we all did.

Well I would rather be safe than sorry, especially on a sealed system.

Burger · Apr 28, 2019

MC78 said:
Well I would rather be safe than sorry, especially on a sealed system.

Ok, up to you. Just don’t forget to add some inhibitor after all that water loss and introduction of fresh aerated water.

Ben-gee · Apr 28, 2019

I always use this method if possible, ever since spending hours trying to refill a badly designed system - running round venting and backfilling with mains etc.
In terms of caution, I always have the appropriate sized speedfit cap nearby in case it lets go, and the trusty Charles hoover. Although only needed once, a faulty aav I hadn’t found in back of airing cupboard, this one I drained.

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Replacing radiator without draining down?

pledgeX

SimonG

Burger

Burger

Aire

Burger

Rob Foster

Rakesh

Harvest Fields

Harvest Fields

SimonG

SimonG

SimonG

MC78

Ben-gee

MC78

Harvest Fields

MC78

Burger

MC78

Burger

Ben-gee

MC78

Burger

Ben-gee

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