Can I change a radiator valve without draining the system ?

[JBrennand]

I removed a radiator in the bathroom to redecorate and refitted at the weekend. I noticed yesterday one or two drips an hour from the cap nut. I tightened up a couple of mm and now it's dripping even more - 1 drip a minute ! Have I damaged the olive or thread ? Should I try tightening further ? I think I know the answer

Anyway, if I have to replace the olive (& valve) as it's the one on the supply side I guess I have to freeze the pipe or drain the system - or do I ?

It's a sealed system with a W.B. combi boiler.

If I lock down all the other radiators upstairs, drain the bathroom one, switch off water supply and then remove the cap nut & valve - will water pour relentlessly out - or, because of the height - will it just lose a pint or so equivalent to what is in the pipes above this radiator ?

If not would freezing be a good option for this ? - job should only take 15 minutes or so I guess.

By the way, if I have to drain the system how do you do this for a sealed combi system - never had one before There is no drain plug anywhere I can see on the downstairs rads and none around the boiler/pipes. Is there another way to do this or did they just not fit a drain valve ?

Thanks for any advice

John

 

[Softus]

I tightened up a couple of mm and now it's dripping even more - 1 drip a minute ! Have I damaged the olive or thread ?

I'll tell you in the morning when my clairvoyance and X-ray vision comes back on-line.

Should I try tightening further ? I think I know the answer

I also think you know the answer.

Anyway, if I have to replace the olive (& valve) as it's the one on the supply side I guess I have to freeze the pipe or drain the system - or do I ?

One or other other, yes.

If I lock down all the other radiators upstairs, drain the bathroom one, switch off water supply and then remove the cap nut & valve - will water pour relentlessly out - or, because of the height - will it just lose a pint or so equivalent to what is in the pipes above this radiator ?

The latter.

If not would freezing be a good option for this ?

Not really. Draining is quicker, simpler, and cheaper, and puts no time pressure on you to get the job done.

job should only take 15 minutes or so I guess.

If your plumbing is as poor as your guesswork, then no.

By the way, if I have to drain the system how do you do this for a sealed combi system - never had one before

You turn off the boiler (i.e. prevent it from firing), then open drain off cock.

There is no drain plug anywhere I can see on the downstairs rads and none around the boiler/pipes. Is there another way to do this or did they just not fit a drain valve ?

If you don't have a drain off cock then you need to drain from a radiator valve, or cut a pipe under the floor somewhere.

 

[namsag]

No need to drain it or freeze it. It can be done by creating a vacum iin the system.
Either close the flow and return isolating valves under the boiler or screw down the auto air vent cap then realese the pressure in the system (through bleed nipple,draincock or by undoing your rad valve) you will get a couple of pints of water come out then it will stop .
You can then change the faulty valve and olive etc.
If it is an old boiler and the isolating valves look dodgy then don`t touch them as they will leak
If you do for whatever reason have to drain it ,pressurised systems don`t usually give any trouble starting up again once properlly bled.

Have a look outside your drainck maybe there or behind an access plate

 

[ChrisR]

100% with namsag.
Your first moves will be the same as whatever you did to remove the radiator.
CLose the boiler valves or whatever as the man says, then you can just open the rad valve, it'll be obvious if you've got the vacuum you need or not.

If you can't easily get the olive off, try a couple or three turns of ptfe tape round the olive, and replace the valve. It's only the side which goes against the fitting which matters.
You won't need to replace the rad to test so it's easy

 

[KateMoss]

Hi, I'm not a plumber but I have replaced a normal rad valve with a thermostatic several times without draining the system. I have a kit which consists of two rubber bungs and you push them into the correct outlets in your header tank then you can remove the valve with no problem. I don't know if this would suit your system but you can get the kit in a plumbers merchant and I am sure they will be able to advise you - or read the instructions before buying. As I say I am not a plumber so apologies if I have misunderstood, but I reckon this has saved me hundreds of pounds to date and it cost about a tenner!

 

[doitall]

Hi, I'm not a plumber but I have replaced a normal rad valve with a thermostatic several times without draining the system. I have a kit which consists of two rubber bungs and you push them into the correct outlets in your header tank then you can remove the valve with no problem. I don't know if this would suit your system but you can get the kit in a plumbers merchant and I am sure they will be able to advise you - or read the instructions before buying. As I say I am not a plumber so apologies if I have misunderstood, but I reckon this has saved me hundreds of pounds to date and it cost about a tenner!

You would have a problem in this case Kate

 

[Softus]

I reckon this has saved me hundreds of pounds to date and it cost about a tenner!

I don't know how you find the time what with all the modelling an' all.

 

[JBrennand]

No need to drain it or freeze it. It can be done by creating a vacum iin the system.
Either close the flow and return isolating valves under the boiler or screw down the auto air vent cap then realese the pressure in the system (.

Have a look outside your drainck maybe there or behind an access plate

Thanks guys - but there are no isolation valves on any of the pipes at the boiler . Not taken the boiler cover off to look inside though. No draincock anywhere to be seen either.

So I think I will go for the approach of isolating the system uostairs

Thanks again, John