I need to replace the toilet connector line in my bathroom (the old one failed catastrophically and flooded everything).

I'm stuck because I can't figure out what size is correct. The pipes are quite old and it appears that the old line used a no-longer-standard size nut to connect to the valve coming out of the wall.

1/2 FIPs is too large, 1/2 COMP is too small. The hardware store near me has a plumbing-specific thread checker board, but the nut on the end of the old supply line doesn't fit onto any of the threads.

I'm adding a photo of the old supply line and the valve -- ignore my temporary Rube Goldberg solution to the problem.

Does anyone have advice on how I can figure out what size I need and where I could buy the correct supply line and/or an adapter?

unknown size nut valve

  • 2
    Rube would have been proud of that ;)
    – Tetsujin
    Commented Nov 1, 2023 at 17:13
  • that is just asking for a flooded home
    – jsotola
    Commented Nov 1, 2023 at 19:30

1 Answer 1


If the valve outlet is an odd size, replace it with a standard one.

It looks like you have a 1/2" threaded connection coming out of the wall. If you can shut off the water to your place (and confirm it's off before proceeding), remove the valve and replace it with a 1/2" FIP x 3/8 compression stop valve. You can then use a standard toilet supply line.

When removing and installing the new valve, be sure to back-wrench the nipple coming out of the wall.

  • Ok, I was starting to think this might be the answer. Thank you!
    – TGW
    Commented Nov 1, 2023 at 17:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.