Draining a central heating system with no drain point

Our central heating system doesn't appear to have any drain points in it apart from possibly on the boiler (which is about 6' off the floor). We've a suspended ground floor with pipework running under the floorboards. Without actually taking up all the floorboards around the 3 downstairs radiators to check that someone installed one - I'm a little stuck.
So - assuming for now that there aren't any under the floorboards - what should I do to drain the whole system?
I'm planning on adding TRVs sometime, so I'll just fit lockshields with draincocks on when I do that. However I've found a leak on a solder joint going to a radiator in a room we're decorating. It's been there since we moved in, but we're going to put down a new carpet - and don't want to that if I'm going to need to take it up again to lift the boards to repair the pipe, let alone if its going to stain the carpet before I do that! Depending on how I feel - I may well do all the jobs at the same time - however I just need to get the water out the pipes first!
I know that trying to solder a joint which has any water in it may well fail - however what about compression joints? Do these need to be completely dry before making the joint?
Thanks
D
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No, in fact you can fit them on pipes with water flowing out of them, which I have taken advantage of several times recently. I'd put an isolating valve on the wrong way round, so I closed it, closed the valves on the radiator on the right hand side of it, and then undid the right side. Bit of water came out. Undid left side, keeping it pressed left, then swapped it quickly, and did it all back up. Caught all the water in a tray.
Ben
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No, compression joints can be done whilst wet. Good job really when we added a new working stopcock to my system that didn't have one...
Don't bother with jointing compounds or PTFE. Compression joints should be made without either, so you rely on the metal to metal bond, rather than some organic compound that might break down over the decades.
Christian.
P.S. I have successfully soldered pipes (15mm, never tried 22mm) with containing water. Drain off what you can (it wicks away nicely with lots of bog roll). Then use lots of water soluble flux and a f*cking big torch. No guarantees. I've never used the bread trick, but am told it can work.
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If you want to get *all* the water out, you'll need a drainpoint at the lowest point - under the floorboards. In my previous house, which had suspended floors downstairs, I fitted a stop-tap under the floor (accessible through a small flap in the floorboards) with the output pipe going out through a vent brick - so that I could collect the water outside.
The pipes need to be completely dry to make soldered joints - but this doesn't apply to compression fittings nor, I suspect, push-fits.
Roger
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I recently did what you are trying to do by using one of those self cutting taps used for the garden hose system. Stick a long washing machine hose on it and i can drain it straight outside, no trays or buckets required.
Mark
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Hmmm.... very very neat idea!!! I like it! Easy enough to do under the floor too at (pretty much) the lowest point!
Thanks for that.
As an aside - is there any problem with running a CH pump with no water in it? Not that I've done it, but I just wondered.
Thanks
D
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Okay... any idea where I can get these cheaply? I've seen one at Screwfix which appears to have a washing machine hose thread on it - are these the same as outside tap threads? I doubt it. I've got garden hose fittings for screw taps which would be nice and easy to reuse.
Thanks
D
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On Wed, 3 Dec 2003 10:17:49 -0000, "David Hearn"

Outside tap fitting sets from Hozelock, Gardena etc. come with various adaptors because there are various sizes used on outside taps. However, the 3/4" washing machine size is one of them and quite common.
You can get washing machine taps and outside tap fitting kits using this "tapping in" method from the DIY stores.

.andy
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On Wed, 3 Dec 2003 09:41:48 -0000, "David Hearn"

Only if you own stock in Grundfos...... :-)
Anything more than a very short "accident" will likely screw it up - typically the bearings.

.andy
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wrote:

Thanks - that's good to know. I had (bizarre) visions of pumping the water around to possibly drain it faster - however, I also realised that it was likely to run dry quickly. Good to know that its not something I should try. Not even sure if it would have done much benefit anyway - certainly not going to experiment!
Thanks
D
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On Wed, 3 Dec 2003 11:39:35 -0000, "David Hearn"

.andy
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