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Shut Off Valves Leaking

I am remodeling my 1st floor bathroom by:
- re-tiling the floor
- painting the vanity and replacing the vanity top

Since I am re-tiling and replacing the top I removed the toilet and am replacing the vanity faucet. Because of this I want to replace the shut off valves with new 1/4 turn compression valves for the sink and a threaded 1/4 turn valve for the toilet (it comes from the floor).

The problems started when I shut off the water in our basement that controlled the water to this bathroom. It also shut the water off to the basement bathroom that was added by a previous owner (toilet and sink, not shower). After about 20 minutes (I had not yet removed the old valves) water started leaking in the basement at the point where the water pipes go through the subfloor into the 1st floor bathroom. It was easy to see that these pipes led to the sink and toilet that I was replacing. Again, at this point I did not repalce the valves, although they were in the off position.

I assumed that there was water in pipes so I quickly opened the faucet in the basement bathroom thus draining that line. The leaking stopped, but there was still a slow very minor flow from the bathroom faucet. Therefore, I kept this faucet opened because if I close it, the leaking starts again.

First question. Is that slow flow in the basement faucet due to the fact that the seperate water line to the shower is backflowing to the other lines?

Next, since there was no water coming the the 1st floor bath, I installed the 1/4 turn valves. For the sink, I used a pipe cutter on the copper pipe and installed the compression fitting. I was careful not to overtighten the fitting, but it is snug. Well, I then turned on the water and after about 30 seconds, water started to leak at the fitting.

I am obviously concerned about the leak. Is it possible the water pressure is too high. I say this only because I once had to adjust a shutoff valve that controlled an outside house bib (water shot out of it like a firehose!).

Any help or suggestions would be greattly appreciated!

Re: Shut Off Valves Leaking

1. Most likely you have a shut off valve that can't fully stop the incoming water. I'd replace it too. The water you saw was also from the backflow, but backflow water ends very quickly. And if you still have a leak, it's the shut off valve.

2. Knowing when to stop tightening a compression nut is something only a skilled plumber knows. You did not tighten the nut enough, that's why you had a leak. Use bigger wrenches, but don't over tighten, or you will damage the nipple/copper pipe.

3. Water pressure can be checked with a guage at different locations in the house. It should read 50-75 psi.

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