Changing thermostatic valve - drain or not.?

[ashtons99]

I’ve got a couple of weeping thermostatic valves ( from the valve insert not the unions.) the wisdom of tik toc seems to suggest it can be done quickly by just putting a folding bucket under the valve and whipping it off and putting the replacement on, obviously using the existing unions and olives.

Is this feasible or is it likely to end with a fountain of water out of both the rad and the feed pipe.

 

[HERTS P&D]

Drain it down.

Andy

 

[Stuckinarut]

What type of system?

 

[ashtons99]

What type of system?

It’s a combi

 

[ianmcd]

Release all the pressure from the boiler then close the drain point used and you will be able to snatch the valves , a little water will come out but not a lot , as long as you close wherever you released the pressure from

 

[Stuckinarut]

It’s a combi

It’s often ok not to drain the full system as a vacuum is usually created

 

[Mottie]

I changed some of mine - sealed system but not a combi. As said, just drain the system until a vacuum is created and then replace the valves. You’ll get barely a dribble out of the pipes/rads. Don’t forget to repressurise the system afterwards.

 

[Dereekoo]

Did sons radiator on combi system by depressurising and then replacing valves one at a time (make sure other valve is closed) have every thing ready and a towel around pipe you are working on. Did the same to other sons radiator with standard header tank system, this time put carrots in header tank pipe feed to central heating and one in expansion pipe outlet to create a vacuum in the system, again straight forward just have everything ready
Oh and actually took the radiator off before working on the valves

 

[ashtons99]

It sounds like I might get away with it or maybe not. Is it more likely to be successful on upstairs than downstairs, I’m thinking gravity ?

 

[terryplumb]

It sounds like I might get away with it or maybe not. Is it more likely to be successful on upstairs than downstairs, I’m thinking gravity ?

Makes no difference.

 

[ChrisJP]

An alternative is to use a pipe freezing kit just upstream from the valve you want to change. You do of course need to drain the radiator first.

 

[dilalio]

Just be aware of AAVs as they can allow air in and stop the vacuum holding.

Including the one in the boiler!

 

[ericmark]

I would say depends on the floor, mother's hall floor was carpet on top of quarry tiles. I got all prepared, carpet washer at the ready to suck up any spills, and swapped a simple valve for a TRV just being quick, sealed system so lost very little.

This house, I would not take the chance of getting the floor wet. As it would damage the floor, even if only a short time.