Main valve replacement

[MasterPlumbersKeymaster]

I need to relocate the main cutoff valve in my house. The 3/4″ copper inlet pipe is laid in the concrete slab and I have to extend the pipe about 3′ to the left so the new pipe will also be in the slab floor for 3′.

I turned the water off at the street only to find that water still dribbles out my basement faucet (which is lower than the cutoff valve) after a 1/2 hour wait. I figure that the whole house is drained after 1/2 hour.

Is there any way for me (homeowner) to plug the copper line in the slab floor long enough to solder the new extension section? Calling the local water utility to either turn off the whole street or replace the valve is last on my list (would take too long).

And is there any special solder I should use on the joints in the slab?

Bruce

[Retired plbg1Participant]

We use to freeze the line with dry ice. Now you can go to Plumbing supplyhouse and get a rubber plug to fit pipe and tighten down and stop water. If you can leave old valve on then install new one where you want it. Take the stem loose on old one and let it drain and solder on new one. Dont completely remove stem just loosen to drain.

[nicktheplumberParticipant]

You could also try the French bread trick. Ram a piece of dried out French bread into the pipe upstrean of the joint you want to solder. You need to act fast, so assemble the new valve and fittings so that you only have to solder one joint while the bread blocks the seeping water. Have everything ready to go and have a really good heat source (i.e., a swirl combustion or primary combustion acetylene torch). The bread will block the water long enough for you to make the joint. It will then disintegrate and can be flushed out of the line when you open the new valve. This is an old trick and it works for all but the largest leaks…

NtP

[Author]

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