Draining down CH pipes underneath floor

Does it matter if the pipes under the floor are full or water?

If the water is drained below the level of the radiator, there won't be any spillage when you disconnect it.

A big car sponge is useful for catching drips!

Markus

Sorry about the blank response - pressed the wrong key before typing! Depending upon how you want to do the job you could always use a pipe freezer kit to avoid draining at all. I've fitted a number of TRV's on my radiators using freezer kits. The ice plug lasts for 30 - 40 minutes which is usually plenty of time to cut the pipe and fit a valve.

Kev

Only if you need to tee into them for the new rad, or solder close to the drain-down level.

Er, yes!

True, BUT the OP wants to add an additional radiator. This will normally require extra branches off the low level flow and return pipes. Breaking into these will cause a flood if they are still full of water.

Question to the OP: Are the pipes under the floor all joined by soldered joints, or are there any compression joints? If there's a compression joint you can get at, this is what I would do: Firstly fully turn off both valves on all radiators to keep them full of water - making a note of the open/closed position of each lockshield, so that you can restore the balance. Secondly, if it's a vented system, put bungs in the fill and vent pipes to keep the water in the F&E tank Thirdly, drain as much of the remaining water as you can, using the drain c*ck which you mentioned. Finally, crack a compression joint under the floor, with a shallow vessel** under it to catch the remaining water.

Someone recently suggested using a WET vac type "Hoover" to deal with this situation, the method being (if I remember correctly), remove rad and drain tap, seal the suction hose on to the pipe with a bit of PVC tape or similar, open up the other rads to let air in and then switch it on, sucking the water into the wet vac reservoir. I've never tried it but it seems like a good idea. if you have the means or inclination to try it, please let us know if it works. Cheers Tom

I don't see why not. Put it in an accessible location with a valve, so you can drain it next time. Obviously, ensure that the free end of the hose is well below the underfloor pipe level and ensure you don't drain using the conventional drain first, or you'll never charge the syphon. The water in the system must be above the level of the highest part of the hose loop.

Christian.

Doh! Yes. I didn't read.

M.

Why would anyone install a central heating system without putting in proper provision to drain it? It seems senseless to me. Are you 100% sure that no other 'main' draincock exists outside?

It is quite common for the pipework below floor level not to have any drainage ability. The same situation existings on my system and almost every system I've worked on. The main difference between those cases is this is that the pipework for me is below a suspended ground floor. It matters little if you just cut the pipe and have the bottom dregs pour away, unlike a flat with more accommodation below.

Christian.

Because if they're not going to flush it through once it's installed what's the point? Can't you spell cowboy?

Tom wrote: please let us

Yes, it works perfectly.

Regards Capitol