I need to replace the stop valve to my toilet but it is connected to a copper pipe from the wall as shown in the photo. I have no experience working with copper pipes. How should I proceed?
enter image description here

  • is it leaking ?
    – Traveler
    Jul 19, 2022 at 19:34
  • 1
    No, the valve is not leaking, it just does not stop water from filling the tank.
    – P Schmurr
    Jul 19, 2022 at 19:36
  • This previous question should have all the info you need to fix this (with pictures!): diy.stackexchange.com/questions/246134/…
    – Armand
    Jul 20, 2022 at 15:24
  • Lots of answers rushing to remove/cut things off, when the valve can easily and inexpensively be rebuilt in place. Just a few standard open-end wrenches needed.
    – Armand
    Jul 20, 2022 at 15:28

6 Answers 6


I would suggest repairing the valve as close quarters like that you may have problems.

To me that looks like a compression fitting if the valve can not be repaired.

With the water main off 2 wrenches are needed 1 to hold the nut and 1 for the valve.

Unscrew the nut from the valve and slip the valve off, It may take some back and forth twisting to remove.

I believe this is compression because I don’t see a sweat fitting or evidence of sweating. The nut facing the faucet is a classic setup for compression where a brass bead, band is compressed onto the copper the nut is trapped but a new compression valve can be attached to the nut

  • 2
    Yup. Looks like compression, and you do not want to cut that pipe any shorter than it is, so get a new compression valve (and take out its nut and compression ring, since you'll be leaving these ones on the pipe) if you can't fix the valve you have. Most important thing is to hold the valve so you don't twist the pipe when taking the nut off (and when putting it back on.)
    – Ecnerwal
    Jul 19, 2022 at 19:29
  • 1
    @EdBeal Thanks, I somehow totally missed that part of your answer - I remember thinking it doesn't seem like Ed to ignore a simple quick fix.
    – Armand
    Jul 20, 2022 at 17:57
  • 1
    If a new valve is needed/used, highly recommend buying a 1/4 turn valve to replace. ( I assume this is not a 1/4 turn valve--- looks like the ones in my home and I hate them).
    – peinal
    Jul 20, 2022 at 19:09
  • 2
    I've replaced every such valve in the house, the new ones have the same thread as the old and the old nut and ring work fine on the new valve. Now, the outside faucets were another matter--the builder used some oddballs and I finally got a tool that would pull the old rings. A royal pain. Jul 21, 2022 at 0:30
  • 1
    Loren , I have cut the brass off in the past but where I had trouble was the copper was deformed , I had to put the new slightly different compression fitting in the same place to keep from leaking we Did 3 homes in 1 track and all the valves were unique we got good at slicing the brass thin enough to crack it and pull the nut off. We had tried everything prior to that even back filling and freezing with dry ice. Cutting with a moto tool and fiber disk worked best for us as there were a Dozen of these valves in each home. What tool did you find?
    – Ed Beal
    Jul 21, 2022 at 0:47

That's almost certainly a compression fitting valve. I've grown to dislike those "twist-in" style valves because they contain a rubber gasket that can corrode over time. They can also be a nightmare to open and close.

If you remove the old fitting (be sure the water is off first!), there will be the nut and compression ring. They should slide off easily once the fixture is removed). My personal preference is to use quarter-turn ball valves (easy to turn off and less prone to corrode in the shut-off parts). If this is the only one you want to replace, spend the extra money and buy a Sharkbite. They are a special type of compression seating that slides on without any tools. Just make sure the end of the pipe is smooth (can use a metal file on it if it's not).

As a final tip: buy a shiny new flange cover while you're at it. They're cheap and yours looks corroded.

  • 4
    Quite often compression rings don't slide off easily. They've spent their lives being tight enough to hold back water pressure by sealing, why should they? That and the nut could easily stay on, and the new tap screwed straight on.
    – Tim
    Jul 20, 2022 at 15:06
  • The rings I have removed put up quite a fight. However, the nuts are mostly standard and don't need replacement. Jul 21, 2022 at 0:31
  • 1
    @Tim: I would go further. If the fitting isn't leaking (the OP says it isn't), compression rings never slide off easily. They are harder than the copper, and tightening the fitting makes them bite into the pipe. Why would the OP not reuse the existing olive? Jul 21, 2022 at 6:53
  • My experience runs contrary to this. (a) Olives do not slip off. Properly tightened, they (correctly) wedge into the pipe at each end. Overtightened, they put a slight neck in the pipe itself. (b) Sharkbites like clean fresh pipe, and have quite fine tolerances. They will not get a proper grip where an olive has previously been. (c) Filing a copper pipe (except to remove a burr at the very end) will result in a leak. At the very most, fine emery paper or steel wool is as rough as you should get. Jul 21, 2022 at 7:34

Get one of these tools to remove the compression ring. It's called an Olive puller and works in tight areas.

enter image description here

  • 4
    There's no reason to remove the compression ring that's on the pipe.
    – Ecnerwal
    Jul 20, 2022 at 14:16
  • 1
    You can gamble. But the risk/reward is not there. Leaks are expensive. Jul 20, 2022 at 23:58

Get a piggy back valve. You keep the existing one in place and just screw the new one onto the threaded end of the existing one.

If you want to just have one then you could shut the main water supply to the house off. Cut the existing one as close to the nut as possible - recip saw or osc tool or hand hacksaw. Sand and debur the copper and put a sharkbite push valve to replace it.

  • Can you add an image of a "piggy back valve" to your answer? I search the Evil Empire (Amazon) for that term, and none of the results used that term. Everything it showed me looked like regular valves. Jul 21, 2022 at 3:36
  • @RockPaperLz-MaskitorCasket It's also called a "repair valve". Any hardware store should carry them - one female end (usually with a captive nut) to fit on a standard 3/8" compression-style outlet of the existing valve, and one male standard compression-style outlet end.
    – Armand
    Jul 21, 2022 at 4:40
  • @Armand Thanks. I searched the Evil Empire for that term too, and nothing in the top of their search results looked like what you describe. Maybe Amazon doesn't carry nearly as many different products as they want us to think. I'll check out a quality hardware store. Jul 21, 2022 at 8:33
  • @RockPaperLz-MaskitorCasket Often you need to already know what you're looking for to find it there :( I added an answer with photos and more description words.
    – Armand
    Jul 21, 2022 at 18:03

Valve repair

Beside other recomendations, do not unscrew the compression seal. They are meant to last life time and not to be broken. During the compression process, the compression ring will make a permanent grove in the copper pipe. Breaking that seal there is not guarantee it will not leak. Cutting it off from coper pipe and replacing with new, is only a option, only if you have enough space to the wall.

It might be something simple like loose handle, not closing the valve. Check the Philips screw and tighten it. To check, use a marker and put a dot on the white shaft. Do you see the dot moving when you operate the handle ?

Alternatively if the main seal is leaking:

Use Philips screwdriver and unscrew the handle.

Unscrew the nut around the shaft of the handle.

Under it you will find the first seal, used to prevent leaking to the outside.

Unscrew/pull out the valve guts.

At the end part there is a second seal.

That one is for water shutoff.

Replace both seals and assemble.

  • Yes, look for something in a hardware or big box store called a "multi turn valve stem repair kit".
    – Armand
    Jul 20, 2022 at 15:18
  • This previous question has the info you need to fix this: diy.stackexchange.com/questions/246134/…
    – Armand
    Jul 20, 2022 at 15:24
  • Compression fittings can be undone and re-tightened may times, without fear of leaks. The key is not to over-tighten them and damage the olive.
    – SiHa
    Jul 21, 2022 at 7:46

This is just to show what a "repair valve" or "piggyback valve" looks like:

Note that the female end has a loose captive nut and inside brass end designed to match the shape of a male compression connection. The captive nut gets tightened down to force the female end and male end together to make a solid metal-on-metal compression-quality seal without any ferrule or gasket or plumbers tape.

3/8-Inch O.D Female Compression x 3/8-Inch O.D Male Comp. A Lead-Free Brass Quarter Turn Water Shut Off Straight Repair Add On Stop Ball Valve,Chrome For Kitchen,Bathroom Faucet

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