Self cutting taps?

We have a downstairs toilet that is being decorated. We want to replace the small sink in there, but the stop-cock for water in the house is deranged (hidden in a very inaccessible place and caked up so its impossible to turn, about 5 cm off the ground (thanks prior botch-up artists!)). Whilst we debate how to resolve that issue, I stumbled across self-cutting taps (is that the right term?).
These seem to be ideal - we could put these on the pipes into the sink to turn off the water and then do the rest of the deed. But its very unclear from the images on the DIY web stores what/how this works. The suggestion is for outside garden pipes, but they look the right size for our pipes (15mm).
Do I (mis)understand...they will cut into the existing pipe, sealing it, allowing us to turn off the water, and then fit appropriate piping/tubing the other side to connect to the taps? Or is it a requirement the water be turned off before using them?
thanks
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On 19 Feb 2004 12:17:22 -0800, snipped-for-privacy@crisp.demon.co.uk (GoogleFox) wrote:

If these are the taps I'm thinking of then you have to bear in mind that they restrict the flow somewhat. That is, in a 15mm pipe they cut a hole of maybe 5mm, so you get quite a lot less water flow.
This is okay for things like washing machines because you aren't bothered if it takes a couple of minutes to fill up. But if you've just popped in the loo to wash your hands it is doubtful that you will be delighted with the time it takes to get a handful of wet soap.
I would deal with the stopcock issue. Do that properly and all other problems disappear.
PoP
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Afraid you are misunderstanding their use. A self cutting tap is merely a way to make a branch off from an existing pipe without needing to turn off the supply or drain out or solder.
To do what you need , you should obtain a good pipe freezing kit , this can 'turn off' the water flow, and allow you to cut the pipe and fit a new stop cock.
However, before all that have a look outside and find the outside stop cock, most properties have one which can be found, estecially if you have a water meter. Turn off the supply and fit a new stop cock, either in place of the original or further inboard. If access is difficult then get a new type remote operated stop valve.
MrCheerful
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They don't cut into the pipe and cut off the supply, they cut into a pipe and give you a supply with a tap. self cutting taps are a way of tapping into the water supply without the need to solder any fittings. They are ideal for the diy'er who wants a quick fix say for plumbing in a washer/dishwasher/ outside tap etc. I suppose you could use them to cut into the cold and hot for supply to the sink, but they are a bit unsightly. these will not help you to stop the mains water, if that is what you are trying to do. Why not stop the water in the street outside your house. Look for the small square metal plate outside. open it, you may need a long fitting with a "U" shape on the end of it to turn the tap. sometimes its just in reach with a long arm. When the water is off, repair the mains stop tap. You can now buy a push fit valve to replace stop taps, with a built on switch. Flick the switch and the water stops, no more turning of taps. You can even put the switch in a more accessible position. rob
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I think you misunderstand (or I do :-)
If they're what I think they are they tap into the pipe allowing you to connect another service e.g. a washing machine or outside tap, but they don't stop the flow of water in the pipe itself.
If you can't turn your indoor stopcock you should be able to find the one in the strret and turn that off to work on your system. You may need a long-handled tool looking sort of like |---------C and you may also find your outside cock also turns off next door's water (or even half the street's!)
(The |-----C tool may be what you need to turn your indoor stopcock off.)
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In an earlier contribution to this discussion,

John is right! A self-cutting tap enables you to fit the equivalent of a tee piece into an existing pipe without turning the water off - e.g. for a washing machine or outside tap. The "tap" part of the fitting controls the flow along the new branch - but doesn't stop the flow in the original pipe!
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