New fridge with 1/4 inch poly line. Unfortunately the connection at the water line is standard copper pipe (1/2 inch). Tried a few different compression adapters from the local hardware store, the threads don't match up on the main water line, so I'm guessing it's a different type of threading? What would be the adapter sizing I would need? (I Don't want to pay a plumber sixty bucks to come screw on an adapter)Water line connection behind fridge placement

Attempted using 3/8 to 1/4 compression fitting, unable to screw onto pipe, seems appropriate size but threading doesn't match up. Here is close up of the threading on the existing pipe

  • In the picture, is the whole silver-colored part your new compression fitting? Are you saying it doesn't fit properly on the copper pipe? Or are you saying what's pictured is your existing pipe + valve and you're trying to attach a 1/4" poly fridge line to it but it doesn't fit? Feb 26, 2016 at 20:10
  • You will pay the plumber more than that!
    – DMoore
    Feb 26, 2016 at 20:32
  • The silver portion is the valve that was attached to the copper pipe when I moved in. I am looking for guidance on the connection of the silver valve to a 1/4" refrigerator line.(Silver valve measures 1/2", 1/4 to 1/2 compression adapter doesn't work as threading on the silver valve is different)
    – user50723
    Feb 26, 2016 at 21:00
  • 1
    Most likely the valve's output is 3/8", and you need a 3/8" to 1/4" adapter. Feb 26, 2016 at 21:42
  • These are standard plumbing supply compression fittings. I think this is the spec sheet for your valve: brasscraft.com/PDF/… Feb 26, 2016 at 22:19

1 Answer 1


The picture shows a copper pipe with a compression-fit valve attached. The copper pipe is presumably just a straight section of pipe going into your wall box, and the silver-colored thing with a shutoff knob is a valve attached to the pipe. Are you trying to replace the valve or use the threaded output on the valve itself?

If the existing valve simply has the wrong size output to attach your icemaker line, then the adapter you need is one that takes this valve's male end and adapts it to 1/4" male. If the existing output is a little too wide, then most likely your existing valve is 3/8" (typical for faucet supplies). So you'd need a 3/8" Female to 1/4" Male fitting like this one.

(Note that the linked fitting includes a compression nut that you would simply unscrew and discard for your application - you'd just screw the adapter to your existing valve, and then screw the line to the adapter.)

Another options would be to replace the valve with a similar one that attaches to your copper pipe but has the desired 1/4" male output. You'd buy a new valve with a similar compression fitting designed for 1/2" OD pipe. This would attach to your existing copper pipe, but you may need to cut it and polish it with emery cloth to ensure it is smooth and circular, so that the compression fitting can attach properly.

  • 1
    I think @shimon just saved you 60. +
    – Ed Beal
    Feb 26, 2016 at 20:35
  • You can just keep the valve, throw on three inches of copper with a waterline adaptor and cap it. If you can't cap the adaptor throw another 2" of copper and cap.
    – DMoore
    Feb 26, 2016 at 20:39
  • @DMoore what do you mean "cap it"? I think he wants to attach an icemaker, but the 1/4" line he has doesn't fit on the valve output. I agree he just needs the appropriate adapter. Feb 26, 2016 at 22:21
  • Most of these adapters are set to hook into 1/2" copper so it is easier to just use one of those for $5 off the shelf and then cap it, opposed to changing out the stop valve which still has use here.
    – DMoore
    Feb 26, 2016 at 23:36

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