Drain central heating when no drain valve?

diyAlex · 14 Dec 2011

We have a one pipe central heating system, and I want to insert a compression equal tee into the supply pipe (and another into the return pipe) to add in some new two-pipe runs.

So I will need to drain down the system.

Trouble is, I cannot find any evidence of a drain valve! This is a bungalow. The combi boiler is in a relatively new part of the property and the one pipe circuit runs along the skirting boards. It ducks under the floorboards in a couple of places, but everywhere I've looked (which is not absolutely every inch of pipe) there is no valve.

So what options do I have? I've looked at self-cutting valves, but can only find 15mm ones.

nogoodatfaultfinding · 14 Dec 2011

turn both Rad valves fully off on any rad, crack nut and drain rad of water (i use pepsi max empty bottle and a bucket lol) once drained use a hose, 1/2 " nut small peice of copper and attach to a closed valve, once attached (and hose is outside) open valve hose is attached to to empty system. Job Done

PlumbGas · 14 Dec 2011

have a look outside first, you may find a drain valve sticking out of the wall, if you're lucky

diyAlex · 14 Dec 2011

This is a very old system and I'm not convinced that the valves and lockshields are working properly. Nice idea though!

And unfortunately no drain valves outside the property either.

I'm thinking about using a pipe freezing aerosol. Freeze a section, put a jacket on it, freeze another section about 4" away and put a jacket on that too. Then get to it cutting the pipe off and fitting the compression tee.

What do you think?

buck51 · 14 Dec 2011

You have a one pipe system!!!!
All your going to do is create problems , if you do as you say.
I think you need to go back to the drawing board.

diyAlex · 14 Dec 2011

buck51 said:
You have a one pipe system!!!!
All your going to do is create problems , if you do as you say.
I think you need to go back to the drawing board.

Yep, we have a one pipe system. And I'm phasing that out. I can't do it all at once. So the plan is to put the two pipe feed/return "artery" down the middle of the bungalow and swap out individual radiators as we can.

So what problems do you think I will be creating? And back to the drawing board to achieve what?

buck51 · 15 Dec 2011

If you put 2 tees in a one pipe system, and create a new loop with rads on it. what makes you think that the loop will heat up,
Without other modifications the heat will just bypass the loop

Andygasman2010 · 15 Dec 2011

It'll be difficult to balance, not advisable really. The two pipe part will take all the heat.

diyAlex · 16 Dec 2011

Thanks for your input, Bucks and Andy. You seem to contradict each other though

What I was thinking (hoping?) would happen, is that the heat would flow to the 2 pipe loop because it is less resistance (initially just one rad on there). And that I could use the lockshield valve to really limit what that rad would take. Thereby achieving a balance (of sorts).

I don't mind if the 1 pipe loop ends up being a bit duff once the 2 pipe has gone in. As long as it works enough to tide us over whilst the 2 pipe rads are fitted (could take several months).

We have an open fire and an electric duvet. We might just have to cope!!

Andygasman2010 · 16 Dec 2011

It all depends where you put the loop. All it is is a path back to the boiler and the water will take the easiest route. Balancing it will be crucial.

diyAlex · 16 Dec 2011

Cheers Andy, good point.

I did have an epithany this afternoon - instead of putting the T's in where the pipe runs around the skirting board in the airing cupboard, I could put them where the pipes run vertical to the boiler (the boiler is the highest point in the circuit. Therefore I will only have to drain the boiler down, and not the actual rad circuit.

diynot

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Drain central heating when no drain valve?

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