Repipe without drain down

[omph]

I need to install a rad, and may need to move the trv a few cm, which means cutting the pipe. Is there any way to do the modifications without having to drain down the whole system ?

 

[kidgreen61]

Yes, it will depend whether you have a pressurised, sealed system, or a gravity fed system as to which method you use,
Either way, you won't be able to solder a joint as the pipe will be full of water.

 

[omph]

Yes, it will depend whether you have a pressurised, sealed system, or a gravity fed system as to which method you use,
Either way, you won't be able to solder a joint as the pipe will be full of water.

Pressurised, sealed. I was under the assumption if I don't vent any of the other rads then suction would prevent a large sum of water from vacating.

 

[terryplumb]

Do yourself a favour and drain down ,to at least a lower level than the pipework you intend to work on.

 

[oldbuffer]

1. You do it at your own risk.
2. In theory, a sealed (and therefore pressurised) system will not leak further from a single point of exit once a partial vacuum has been established. In practice, a faulty automatic air vent, or a slight leak at a joint, can break the vacuum. If you know what you are doing, you can cap the leak / work very fast or whatever it takes to cope with it. If you are less experienced you may no know what to do and get wet.
3. If you are going to try it:
3.1 Close both valves and empty the radiator.
3.2 Slacken valve to pipework nut, drain until water stops flowing.
3.3 Remove valve and install new one. Make sure it is closed.
3.4 Repeat for other valve if required.
3.5 Do not try and remove both valves at once.

 

[omph]

I will obviously drain down that pipe section, I just don't want to have to drain down every rad.

 

[terryplumb]

1. You do it at your own risk.
2. In theory, a sealed (and therefore pressurised) system will not leak further from a single point of exit once a partial vacuum has been established. In practice, a faulty automatic air vent, or a slight leak at a joint, can break the vacuum. If you know what you are doing, you can cap the leak / work very fast or whatever it takes to cope with it. If you are less experienced you may no know what to do and get wet.
3. If you are going to try it:
3.1 Close both valves and empty the radiator.
3.2 Slacken valve to pipework nut, drain until water stops flowing.
3.3 Remove valve and install new one. Make sure it is closed.
3.4 Repeat for other valve if required.
3.5 Do not try and remove both valves at once.

The op needs to cut into pipework and extend it, not just change a valve.

 

[terryplumb]

I will obviously drain down that pipe section, I just don't want to have to drain down every rad.

How are you proposing to drain just the section of pipe ?

 

[Notch7]

Do plumbers ever use freeze kits?

they always seem a bit scary to me

 

[omph]

How are you proposing to drain just the section of pipe ?

Draincock.

 

[terryplumb]

Do plumbers ever use freeze kits?

they always seem a bit scary to me

Yes ,every time premises have no external stopcock and the internal stopcock is goosed, which seems to be quite common in my neck of the woods.

 

[terryplumb]

Draincock.

Great ,where is the drain cock in relation to the pipe you intend to cut into and extend ?

 

[omph]

Great ,where is the drain cock in relation to the pipe you intend to cut into and extend ?

Underneath it.

 

[MJN]

Pressurised, sealed. I was under the assumption if I don't vent any of the other rads then suction would prevent a large sum of water from vacating.

In my (albeit limited) experience, the theory works perfectly in practice when your house is undergoing renovation and has no carpets down. Introduce carpets and the laws of physics seemingly get changed and it's anyone's guess what which actually happen then...