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  1. #1
    Join Date
    Feb 2012
    Vandergrift, PA

    Unhappy 7/16" coupler for water?

    I came home to a watery mess in second floor bathroom the other day. I located the leak at a coupler under the faucet. The inch galvanized supply line was threaded back in the day to fit 7/16 threads. I went to the local plumbing only to find out that 7/16 inch couplers and valves are not made anymore. A nice plumber in the store said that it would be best to take the steel pipe out and put in PVC. The main plumbing is copper but it is unknown how it goes from copper to the galvanized. The plumbing from the basement to the second floor runs through the living room wall but the pipes below the bathroom are above the old slat and plaster ceiling in the living room. Eventually I would like to replace all the plumbing in the house to PVC since every faucet and toilet have a mixture of copper, cast iron, old pvc, and galvanized steel. This leaky sink is the third plumbing problem to arise in this bathroom and is really starting to get to me. Any advice on how I can fix the leak?

    Thanks and blessings,
    Optimistic New Homeowner

  2. #2
    Join Date
    Feb 2012

    Default Re: 7/16" coupler for water?

    Ok you may have to cut a small hole around the coupler and see what is behind the wall more than likely from my experience you will be able to unscrew the existing coupler and screw in a new 1/2" in place that has 1/2" threads on both sides Im betting that yours is 1/2" x 7/16" and then you can convert from there over to shutoff or what need be if its copper then solder on a coupler and extend and put on a compression stop.

    Orem Benjamin Plumbing
    153 N Garden Park Orem UT, Orem, UT 84057
    (801) 960-1565 ‎

  3. #3
    Join Date
    May 2008
    Pacific Northwet

    Default Re: 7/16" coupler for water?

    I've never heard of 7/16" pipe. If that's the actual outside diameter of the pipe, then it probably has a different name.

    For "iron pipe size" (IPS -- galvanized steel, black iron, brass, ABS, PVC), what's known as "half-inch" pipe actually has an outside diameter of about 7/8". 3/8" nominal has an outside diameter of about 5/8". 1/4" nominal has an outside diameter of about 1/2". 1/8" has an outside diameter of about 3/8". The threads on steel pipe are tapered; the very end of the pipe is slightly narrower than the portion where the threads meet the unthreaded portion.

    For "copper tube size" (CTS -- copper, most plastics except ABS and PVC), 3/4 is 7/8", 1/2 is 5/8", 3/8 is 1/2", and 1/4 is 3/8". CTS pipes are typically not threaded, but rather use "slip" fittings that are either welded (via solvent or solder) or compression fittings.

    Are you sure it's not really a standard size? You can't go by the actual measurement; you have to take the measurement and convert it to a nominal size.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  4. #4
    Join Date
    Jul 2010

    Default Re: 7/16" coupler for water?

    The pipe and fitting sizes are not that difficult, but the confusion always starts with "outside dimention" and "inside dimention".

    If there is a leak in a galvanized fitting, replace with "exact same size", or do what plumbinjim17 suggests.

    As far as I know, there is no 1/2"x7/16" galvanized coupling stock sale available. You may find angle stops (on the 'out' side) and supply lines in that size.

    If you have a 1/2" nipple coming off the wall, you don't need a coupling at all. Simply put a flange around the nipple, thread an angle stop (1/2") and a flexible supply line. Turn main water on and check for leaks.

    Hope this clears some of the confusion.

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