The cold water shut off valve under the bathroom sink will not completely turn off no matter how hard I turn it. There is a slow leak.

I know this because I have had the faucet off for several days and the feed line is always full of water on that side (versus empty on the hot water side). I estimate that about one drop per hour emerges.

How can I replace the shutoff valve under the sink?



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You will need to turn off the main supply to the house. That is probably located near the meter. In warm climates where the meter is at the curb, the house shutoff can be just outside the front of the house, or often in the garage.

To further complicate the job, that shut off is often a gate valve which after years of non-use will also leak by.

Now, you need to determine on that shutoff under the sink, how is it attached to the pipe from the wall. It could be soldered, it could be screwed on to a threaded pipe, or it could be attached to a copper pipe by a compression nut. If you have plastic pipe, that opens up a few other possiblities.

If you could post a picture of it, we could offer more advice on how to proceed.

I found the house turn-off valve by the water meter. The city guy came within 10 minutes of me calling and showed me where it was and how to turn it on and off. No charge. That is service!
I took a photo of it but it is over 2,000 kb and I don't know how to scale it down for posting here.
I believe I see a tiny bit of copper coming out of the wall followed by a compression nut, then the supply line, then the turnoff valve.



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Upload your picture onto [www.photobucket.com] amd post the url back here in this thread. following the posting instructions below the post new message box on the post new message screen. Scroll down.

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[i226.photobucket.com]
Above is the link to a photo of my faulty valve.

I wouuld like to know how to replace this shutoff valve.



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I have turned off the main water supply to the house.

The shutoff under the sink is attached to a copper pipe by a compression nut.

How do I get the supply line off?
How do I get the compression nut off?

Help! I seem to have put a hole in the supply line trying to get it off and so my water must stay off until I resolve this problem!!!

photo: [i226.photobucket.com]



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redwood seems currently unavailable, so i'll help since you're in a pince till then.
go to hardware or big box and get a 5/8" compression stop for copper pipe. Leave nut and ferrule on copper pipe after unscrewing stop. you can cut or break the supply line coming off the stop and feeding your toilet. get a new steel braided supply for toilet that matches the outlet of the stop you pick out. remove nut and ferrule from new stop and screw on to existing nut and ferrule. you want to make it wrench tite with wrench on stop and nut. put some muscle to it but don't strain.
hope this helps

since this is under a BATHROOM sink....
go get a 1/4 turn 90 deg X 3/8 stop..
measure the approx distance from the stop to the bottom of the faucet body..
get a faucet X 3/8 stainless supply line that approx length..
put a pan under the faulty valve..
have the new valve ready to install (minus nut and ferrule)..
no tape or pipe dope..
remove old valve..
install new valve and supply to sink (gonna need a "basin wrench"..
don't overtighten..

good luck

This is a bathroom sink. Does that make a difference in your instructions?

no but make sure you dont over tighten the nut on compression fittings. they tend to leak if to tight as with to loose but to loose you can tighten it a bit and get it to stop leaking

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Redwoods back... Was off doing some plumbing work... Pays the bills ya know!

Looks like the advice is spot on! Just be careful not to over tighten that compression fitting its the death of them. I always give the inexperienced the advice to just snug it up then turn on the water and just tighten to the point of no leak. That should get you to not over tighten the fitting.

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I think I have the parts that were suggested. You tell me:

I have a quarter turn angle valve that is 1/2" F.I.P inlet and 3/8" O.D. outlet, solid brass.

I have my choice between 2 stainless steel flexible faucet supply lines, 20". One I bought and one I found in my garage. One is 3/8"OD inlet x 1/2" FIP outlet. The other is 1/2" iron pipe to 1/2" threaded faucet.

Is there anything else that I could possibly need?

I seem to not be strong enough to get this unscrewed and so have called a friend to come across town to try. I have a 440 channel lock and a small vice group. Any other tools I should quickly run out and buy?

I think that using one wrench to hold the supply stop (to keep it from turning around) while using another to tighten the nut is a good idea. Doing this makes it less likely for you to be applying a twisting force upon the copper pipe coming out of the wall.

When using a wrench to tighten it is better to be pulling it rather than pushing it.

When using two wrenches: one to hold the fitting and the other to tighten a connection, it is good to have the opening of the wrenches towards each other and to have the wrench handles in a position of being less than 90 degrees from each other on the starting motion to tighten a connection.

My immediate problem is that I do not know how to get off the old valve and the old supply line.

You need a 1/2" compression inlet valve!

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Edited 1 times.

ericsandstone said, "I think that using one wrench to hold the supply stop (to keep it from turning around) while using another to tighten the nut is a good idea. Doing this makes it less likely for you to be applying a twisting force upon the copper pipe coming out of the wall."

with compression valves you have to hold the valve while turning the nut or it wont tighten. there is nothing to worry about with twisting the copper unless you are tightening an fip valve which does not have a nut

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First, let me suggest that if any of the supply lines in your other faucets in the house are this one piece valve/supply line arrangement, put this on your list for projects to do....soon. As I believe you mentioned has already happened, they are prone to sudden failure if touched. Anyway, once you get the hang of it, plan to do all of them.


Yes, you should hold the valve steady and turn the nut, both for install and removal. Could you do it the other way....hold the nut and turn the valve? Probably. Everyone just does it the first way.

Good advice has been mentiond a few times about not overtightening when installing the new one. You can damage the copper, the nut, or the ferrule, and cause a leak. Basically, I would get it on hand tight, then go half a turn with wrench. If this feels snug, turn on the water and try it. If you get a drip, or if it just feels loose, continue tightening in 1/4 turn increments.


One glitch which can possibly arise....there are some older brands of valves which have coarse threads on the inlet compression nut. You won't know until you get it off and compare new to old. The difference will be immediately obvious if you have this. If you do have a coarse thread, then it will be necessary to remove the old nut and ferrule. Post back for further instructions.

I googled that and do not find one on the web as I wanted to take a picture of it to the store with me.
is it called by another name also?

Just make sure they give you a 1/2" compression inlet X 3/8" compression outlet, 1/4 turn stop valve.

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Just ask for it. The store will have a hundred of the one you want compared to a couple of any other style.

most of the big box stores and hardware stores id the proper stop as 5/8" od compression inlet. Their 1/2" compressions stops are meant to fit 3/8" copper tube. Just tell your smockman your attaching to 1/2' hard copper pipe, which is 5/8" od (outside diameter). I know that's confusing, but it's the kind of thing we get paid to know.

Oops my bad Its 5/8"

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They are labled on the box as 1/2" nom. (i.d.), by 3/8 (o.d.) compression.

Ah so I was sort of right.

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