I was going to remove my toilet angular shut off valve to add a 1/2 inch PVC T fitting. When removing it I noticed that it is a what I believe a compression fitting.

What would you recommend I do to be able to attach a 1/2 fitting; one for a PVC pipe and the other for the toilet shut off valve.

copper pipe

The pipe extends about an inch from the wall and the nut freely spins and cannot remove it.

3 Answers 3


You need to get a compression to pipe thread adapter, then you can use whatever threaded fittings you want. For 1/2" copper, the outside diameter is 5/8". You would need a 5/8" compression x 1/2" male or female pipe:

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  • So this should work on the pipe?
    – Rick
    Mar 26, 2019 at 19:34
  • It should. Check the thread on the compression side of the fitting by removing the nut from the new fitting and screwing it onto the old valve that you removed. Be aware that there were some stop valves made that did not use standard compression threads on the 5/8" o.d. side, they had a proprietary thread that is (noticeably) more coarse than regular 5/8" comp.; I don't think yours is one of those (for several reasons). Mar 27, 2019 at 4:38
  • I got the 5/8 compression to 1/2 inch adapter, but it was very loose. The ferrule never really grabbed the pipe. I noticed that the nut that I removed with the puller was very thick and didn't have a ferrule, so I reused it. The T fitting was loose, but never leaked.
    – Rick
    Apr 4, 2019 at 17:01
  • I did not mean for you to remove the existing ferrule and nut. You should have been able to remove the nut and ferrule from your new adapter and then screwed it directly, using the old existing nut and ferrule still on the pipe... and giving it a good tightening. I have done this many times. Apr 5, 2019 at 17:30
  • I didn't get a chance to take a picture of the old nut itself which is very thick and has like a copper core. I tried putting the new ferrule on the pipe, but it wouldn't fit under the nut using the adapter. The nut wouldn't grab the adapter with the ferrule in between. Here are some pics. It has had 30 PSI and hasn't leaked yet.
    – Rick
    Apr 6, 2019 at 9:45

There are many ways to do this, one is to solder a new adapter or t to the tailpiece you left. Another is a product like shark-bite.

  • 1
    Can I properly solider when the nut won't come off?
    – Rick
    Mar 24, 2019 at 22:51
  • If done correctly, yes. Solder fills in the gap between the pipes. Flux and solder/braze and the solder should flow down the pipe into the fitting and not just fill the visible gap. Why would the nut not come off? Can you cut the drywall in that location and get back further? The shark-bite type fitting would also need a certain amount of pipe to "Bite" onto.
    – Jeff Cates
    Mar 24, 2019 at 22:54
  • The nut won't come off because the ferrule is on the pipe. From the looks of things getting it off will be an adventure. Mar 24, 2019 at 23:30
  • The wall is concrete. In the meantime I'm trying to put it back together, but the nut is spinning freeely and no matter how much I try to tighten, it is leaking.
    – Rick
    Mar 25, 2019 at 0:01

The metal ferrule makes the seal on the pipe. Once compressed they are difficult to remove. The main reason these leak is from over tighting. Since your pipe is locked in concrete a shark bite or sweated fitting may be the easiest path forward. I have used a dremel to cut the nut off in the past then sweated new fittings and valves in tight or places like this without much of a stub out.

  • If I manage to remove the the ferrule and nut with a puller, can I install another compression fitting?
    – Rick
    Mar 26, 2019 at 14:52
  • Possibly you will be able to install a new one if the pipe is not two deformed and if you can get the new one to seal. I have had leaks multiple times when trying to stay with compression fittings, so I don't try I just cut the nut and use ether a coupler sweated on or a push on fitting like shark bite. The copper pipe is soft and using a puller may make it impossible to repair without replacing the pipe if it gets out of round or flared. I usually leave the ferrule in place now but used to remove them.
    – Ed Beal
    Mar 26, 2019 at 15:09
  • I've never used any SharkBite stuff. Not sure if it would go all the way in if I remove the ferrule and nut. The pipe extends about an inch or so.
    – Rick
    Mar 26, 2019 at 16:34
  • I have had a few successful replacements of compression fittings if you can get the nut and ferrule off without deforming the pipe make sure the new ferrule is slightly closer to the end of the pipe so you will be compressing the new ferrule on pipe that is not already compressed. Make sure to not over tighten, take the nut down hand tight then 1/2 to 3/4ths a turn more and check for leaks.
    – Ed Beal
    Mar 26, 2019 at 16:44

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