So in another thread this week I asked a question about the type of valve I need but I ordered the wrong size...uggh.

I ordered this tee connection because it included a shut off valve...which I like.

The new valve thread (3/8") is too big for the existing nut. Can someone help me confirm the correct size I need this time?

Half inch (see photo) minus 1/4" for threads = 1/4"...?

enter image description here

2 Answers 2


1/4" NPT fittings have a nominal outside diameter of just over .5". That's what you have.

  • 1
    3/8 and 1/4 are your only real options so I would say Isherwood is right. Since 3/8 did not fit.
    – Ed Beal
    Apr 1, 2020 at 23:31

That brass fitting you are measuring is not a tee but looks like a compression fitting. If it is a compression fitting a pipe fitting will not screw onto it. A better explanation and a better picture of what you are trying to accomplish is needed.

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