Capping an old lead supply under a concrete floor


Postby theclague » Tue Dec 16, 2008 12:05 pm

I own a victorian mid-terrace in Birmingham that my wife and I have been renovating for what seems like an age (well about 18months). Some months back we removed the old kitchen sink and in the process the old lead rising main pipe was twisted and it began to leak under the concrete floor (producing a constant hissing noise). We contacted severn trent who eventually fitted us a new connection in plastic, but we were responsible for capping the old supply. This old supply is under the kitchen floor and is the last in one in a chain of 4 on a shared supply (where all other houses still use theres).

Over christmas I am hoping to dig up the kitchen floor and find the lead pipe to cap it off but I have a number of questions before I begin. If anyone could answer one or more of them I would be very appreciative.

1 - At the moment there is no visible water leaking (although signs of damp) and I had hoped this meant the split in the pipe was hairline in size. Is this asssumption correct or when I get to the pipe will I get soaked?

2 - What would be the best way of capping the old supply? - I had thought of using a leadloc connection - if the leadloc doesn't work what are my other options (my concern is that I will have to isolate my neighbours water too so I cannot risk having it off for hours while I try to solve the problem

3 - Although I am a reasonably competent DIYer I am willing to pay a tradesmen where it is required - would I be better digging the hole (to keep labour costs down) and then just pay a plumber to come and cap it off?

Thanks for any help in advance.
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Postby plumbbob » Tue Dec 16, 2008 11:28 pm

Whether you get wet or not is anybody's guess, but you could see how you go and be prepared to turn the water off (well you're going to have to anyway).

Yes and the easiest way is to use a Led Lock and get a blank olive to cap the end off.

Having said all this, you want to think carefully about where the pipe should be capped off. There is a good chance the pipe is split in several places so the only way to deal with it properly is to dig a hole outside and cap it off there so it is guaranteed there will be no further leaks under the floor. Digging a hole in in a floor most likely will damage the damp course so should be avoided.

Also, you are not supposed to just cap off a run of pipe. The water trapped in the leg is referred to as "dead water" and may lie dormant in the pipe for many years. It may subsequently become stagnant, and contaminate the drinking water supply.
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Postby Steve the gas » Wed Dec 17, 2008 7:23 am

Hi,


1. Lets hope its water and not gas!! Wear a water proof coat.Joking, if its isolated - it will only trickle.

2.Leadloc is the way - make sure you get the right one. Tell the merchant the dia of the lead pipe.

3.Yes, you sound a little nervous.


Hth
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Postby theclague » Thu Dec 18, 2008 10:27 am

[quote]Having said all this, you want to think carefully about where the pipe should be capped off. There is a good chance the pipe is split in several places so the only way to deal with it properly is to dig a hole outside and cap it off there so it is guaranteed there will be no further leaks under the floor. Digging a hole in in a floor most likely will damage the damp course so should be avoided.[/quote]

I tried digging a trench across the full length of the rear of the property and found that the pipe does not leave the rear so it must run under the boundary wall and under the floor of the neighbours. I suspect once capped I will relay the whole floor, damp course and all, as it is rather poor anyway.

[quote]Also, you are not supposed to just cap off a run of pipe. The water trapped in the leg is referred to as "dead water" and may lie dormant in the pipe for many years. It may subsequently become stagnant, and contaminate the drinking water supply.[/quote]

My intention was to cap off the supply at a tee and leave only my outside tap left on this supply (I have a new MDPE supply for everything else). This way when I used it, it would prevent stagnatino in the dead section.

Thanks.
theclague
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