The main line coming into my house is 7/8 inch copper, .99 OD. I can't find any 7/8 fittings other than a reducer to 3/4. Seems like a 1 inch fitting would be to big, whats on there now is tight fitting as you'd expect from any matching size pipe/fitting. The main shutoff valve needs to be replaced and I don't want to torque it as much as it would take to remove the current one. Currently it has a 7/8 to 1.25 FIP, 1.25 to 1 hex nipple, 1 inch regular port valve. Pretty sure the valve is the original 40 yr old.

Edit: Title updated

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  • 1
    What's your question, exactly?
    – isherwood
    May 27, 2021 at 20:36
  • Does someone know where to get 7/8 inch fittings? Or does a 1" fitting work and if so is it common practices now days?
    – Joe
    May 27, 2021 at 22:03
  • What type of copper tubing and pipe are measured differently pipe is measured on ID. tubing is measured on OD and yes I have seen tubing used as a supply.
    – Ed Beal
    May 27, 2021 at 22:18
  • @EdBeal Sorry not sure if there was a question in there. I suppose to be totally accurate it would probably be classed as 1" tubing. The main supply is was a roll of 1" OD copper to the curb stop. The only fittings I can find (home depot, ect.) are for 1" ID copper pipe (think that's worded right).
    – Joe
    May 27, 2021 at 22:31
  • Wow, that's a flare fitting on the incoming copper. I bet it is 1" tubing... May 27, 2021 at 23:10

1 Answer 1


In the US, copper "refrigeration" tubing is measured by the O.D. whereas copper pipe sizes are nominal (in other words sized by nomenclature where nothing actually measures to the named size). There is no 7/8" pipe, but there is 1" OD tubing.

It would be very odd to have a copper tubing main line, but odder things have happened. I suspect that, if indeed you are working with tubing, it is a repair that someone cobbled together at that section (rather than the entire main being tubing) because they had some 1" OD tubing on-hand.

It is unclear exactly what your question is, but somebody already converted your tube to FIP (at least on one side) so you should use that; on the other side get a 1" compression fitting to convert to pipe thread as well.

  • I'll see what the plumber says I guess. Wanted to have a fitting on hand and just replace it, like I said I don't want to torque the line as that would be the end. I couldn't wouldn't afford to repair it. It's impossible for the current stuff to be a repair job. Slab on grade and I gutted the whole house 2 years ago. Foundation hasn't been touched.
    – Joe
    May 27, 2021 at 22:50
  • To emphasize: There is copper pipe and there is copper tubing , they are different sizes although they may look similar. Jun 27, 2021 at 16:02

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