One more plumbing question and I promise that's it.

I've got one more plumbing question that I'm sure I'll get an instant answer to on here :-) - I've look through the archives and can't really find much on the subject.
In the process of installing a new bathroom, from scratch, I need to take a feed for the hot and cold water from some existing pipes under the floor (which used to lead to the old kitchen taps). The trouble is I'm in an upstairs flat so can't afford to risk water spillage when I cut into these pipes.
I could attach a hose to the lowest tap in the house, stick it out the window and attempt to siphon the water out the system, but I really can't see this working. I haven't heard great things about pipe freezing kits, and even then I still need an area of dry pipe to solder the new connections onto.
Any tips for a task like this?
Cheers,
Andy
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Pecanfan wrote:

Drain what water you can from the system by conventional means, then arm yourself with lots of old towels and some small shallow trays if you can find any that fit (foil food trays can be good) and a bucket. Line area under pipe with old towel to catch drips, and place tray under pipe. Make a small nick through the pipe with a hacksaw. That way you can control water egress by sticking your thumb over the hole (if you dive straight in with a pipe cutter you may end up with more than you bargained for)! Then just fill a tray, stop the flow of water, empty and replace. Keep going until the pipe is empty. Remember you may get a little extra out of the pipe when you finally cut through.
--
Cheers,

John.

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Cheers John - I was afraid that might be the case :-). Think I'll put some plastic sheeting under the towels too - just to be on the safe side. I've got approx 4" between the pipes and downstairs' laths so should have enough room for the trays.
Just thinking, I've capped off the old kitchen tap pipes which are in the same room (kitchen becoming bathroom) - these need to come out 'cause they're in the wrong place but I've just put compression fit end-caps where the taps used to be for now. I wonder if I turned the water off, opened the current bath taps (bathroom becoming kitchen) and removed the end caps from the old kitchen taps whether I could blow some water out the system? The pipe run between the two points is probably about 15m. Or is this a silly idea?
Andy
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Pecanfan wrote:

It is unlikely to get all the water out, although it may shift a bit more... Oh, and you will probably need to use a compressor to supply the air! (using for example, a air duster nozzle and a cloth round the pipe to create a airtight (ish) seal)
--
Cheers,

John.

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Pecanfan wrote:

Why can't you just turn the stopcock off and turn all the taps on?
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Because it won't empty the pipes of water. The water will present itself to the flat below's lightbulbs.
Christian.
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In an earlier contribution to this discussion,

As far as cold is concerned, turn off the water at the main stopcock (probably under the kitchen sink) and open a downstairs *and* an upstairs tap. The pipework will drain through the downstairs tap, with air being admitted through the upstairs tap.
With the hot system, you have to remove the pressure by stopping cold water getting from the header tank into the hot cylinder. Hopefully there will be a tap or gatevalve in the cold feed to the cylinder (the one which comes down from above and goes into the *bottom* of the cylinder. If so, turn that off and then open an up and a down hot tap - as for cold - to drain the pipework. If there *isn't* a valve in the cold feed, you'll need to reach down into the header tank and stuff a tapered cork into the outlet pipe. [Choose one of a size which leaves enough to catch hold of to pull it out again when you've finished!]
--
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It's an upstairs flat!

water
be
that
It's a combi boiler (sorry, didn't tell you that bit)
Cheers though! ;-)
Andy
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Pecanfan wrote:

That makes it simpler in this case....
--
Cheers,

John.

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In an earlier contribution to this discussion,

Sorry, I missed the 'flat' bit - and assumed you had access to downstairs. Do these pipes feed anything below, or not. If so, what I said is ok - if you negotiate with the person below.
If not, and if the pipes you are breaking into are at the lowest point, you'll have to use towels and trays as suggested by someone else to collect the water in the pipes having first turned everything off.
--
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We're on a separate water supply to downstairs. :-)
To be fair that's a recent development - it was shared with downstairs - what a nightmare that was by the way... we actually have water pressure now - woohoo!
Andy
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Pecanfan wrote:
i was soldering a hot water pipe and couldnt stop the trickle of water from the pipe, i did exactly as you suggest,blew down the pipe, it worked. Any water left in the pipe will make a good soldered joint very difficult if not impossible to make, you might consider a push fit fitting for your final connection.

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OTOH, despite stories and myths about this, I've never had the slightest problem soldering joints in previously wet pipework. It's important to have a good torch, though.
Christian.
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Christian McArdle wrote:

A little wetness is usually ok, it will soon boil off. A continuous trickle however is likely to mess it up.
In those situations the old trick of stuffing a ball of fresh bread up the end of the pipe will usually halt the trickle for long enough to solder it. It will wash out the pipe next time you turn a tap on.
--
Cheers,

John.

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With it being a flat, I'm slightly nervous about having compression or push fit joints under the floor, especially since it will be tiled upon and a right b*****d to lift at a later date. I was planning on having pretty much all the plumbing boxed in above the tiles (so my task with these water pipes is to get them popping through the floor at a convenient point, from which point I can feed them 'round to the shower, bath etc.). Hence wanting to make it a solder connection if possible, although know what you mean - might be difficult to get a dry piece of pipe to start on - here's hoping! :-)
Andy
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Some people would suggest the "bread" technique. This basically means shove a bit of bread up the pipe to dry the pipe out. Then solder. The bread quickly degrades and is "potable".
In my case, however, I've had perfectly acceptable results without bothering. I use a good proper sized torch, though. Not a little taymar intended for paint stripping. Obviously, get as much water out as possible first.
Christian.
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Pecanfan wrote:

No need to worry, if it does leak, you will be able to fix the pipe through the hole in the ceiling downstairs... ;-)
--
Cheers,

John.

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push
much
Thanks for that John. :-p
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In an earlier contribution to this discussion,

I've just had another thought!
If you're inserting tee's into the existing pipes, you'll have to cut a short section of pipe out. Suppose you get a couple of those self-piercing washing machine taps (can you get them for 22mm pipe if necessary?) and install them temporarily where the tee's will go.
You can then use the taps to drain the pipes - under controlled conditions - into shallow trays. Finally, when no more water comes out, remove the taps and cut out the pierced section of pipe.
How does that grab you?
--
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.

collect
And resolve never to throw away the foil trays that some frozen food is sold in. They come in very handy for such jobs including, but not limited to draining washing machines -when the pump fails even if it's only fluff. Because such foil-trays tend to be shallow -and awkward to handle / lift when half-full; it's useful to have several so one can be receiving drainage while the other is being emptied.
--
Brian
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