Hi I have a pressurised heating system. I need to change a radiator valve. Is it possible without draining the central heating. I have attached pictures of my pipe work. I am not familiar with plumbing so please make explanations simple.

pipe work


  • Thank you for including pics! It's a detail many forget. Unfortunately, you seem to have posted the same picture twice. If you intended to post two different pics, please edit and try again.
    – FreeMan
    Dec 16, 2022 at 12:23
  • Better! Thanks.
    – FreeMan
    Dec 16, 2022 at 13:12
  • Can you add a photo of the radiator with the bad valve? Try to show the whole radiator, the vale, and the feed and return pipes. And tell us what floor it is on and how many floors there are.
    – jay613
    May 15 at 14:55

2 Answers 2


If you have no other way to shut off the water to a location, you could always freeze the pipes both sides. Kits come in various qualities from 'simple spray can & wrap' to 'I need to do this every day' in prices from $£€ 20 to $£€ 1,700. You may be able to hire one of the better kits if you find the spray inadequate.

Example from UK builders' supply merchant

  • Just to confirm, I freeze below the valve of the radiator then continue to change the valve. Does freezing cause any issues to the heating system?
    – james
    Dec 16, 2022 at 13:11
  • Yeah, @james, you'll have to turn off the heat and let the pipes cool enough that you can actually get them to freeze. Then, you'll have a slug of icy water that'll cool wherever it goes until it warms back up once the heat is turned back on. You'll spend a few extra units of currency reheating the water, but it's probably cheaper and faster than draining the whole system.
    – FreeMan
    Dec 16, 2022 at 13:14
  • You freeze a clear, straight bit of pipe either side of the section you need to shut off - the expansion tends along the pipe so it doesn't burst it. You still need to partially drain the radiator, depending on whether the valve is top or bottom, of course, & refill afterwards [when it's all melted again].
    – Tetsujin
    Dec 16, 2022 at 13:16

Looks like you have circulating hot water radiators.

If you are changing a radiator valve, and you want to use the freezing method, you will need to freeze the pipes on either side of the radiator. It's not like fixing a broken pipe where you freeze either side of the damage. The radiator has two attached pipes and you'll need to freeze the both, as near to the radiator as possible. If the radiator is on the ground floor and you have an unfinished basement there is some chance you can access those pipes in the basement ceiling. Otherwise it's very unlikely to be a viable approach. Also, you'll have to deal with the radiator itself, which is full of water, dumping out through the valve when you remove it. Maybe you can catch a lot of that in a bucket, I don't know. Or maybe it's a tiny radiator with not much water in it? I wouldn't try this.

I think you pretty much have to empty the system to change a radiator valve.

If it's a second floor radiator you can try to half-empty the system, that is, empty it until the water level is beneath the second floor. There's no elegant way to determine that, though. You can run a first floor bleed valve into a bucket, and when it stops bleeding you know the water level is around the top of the first floor radiators, then you can stop emptying.

If it's a first floor radiator you'll need to just empty the whole system.

I have never in my life seen a professional plumber try to "Save time" by not emptying a system before opening it up. My reading of all their combined decisions, along with my understanding of the risks, tells me it's not a time-saving approach.

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