Kitchen shutoff valve sizes

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by greekguy7, Feb 13, 2019.

  1. greekguy7

    greekguy7 Member

    Jul 1, 2005
    Kitchen shutoff valve sizes
    Author: greekguy7 (IL)
    I went to put in a Moen faucet that had the supply lines already attached: 3/8" compression connection at the end of them which is very typical application.

    It turns out the shutoff valves I had in there were 1/2"compression on the end. Darn! Went to get some adapters to go from 1/2" compression to 3/8" compression and one of them dripped so I changed out the entire shutoff valve, and was on my way.

    You see a lot of shutoff valves in kitchen or baths that are 1/2"? Seems like most are 3/8". I think the reason the adapter leaked on one of them is because I was in a hurry and messed up the rubber o-ring that came with the adapter. Is that what makes the actual tight seal connection?
  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    Without seeing what you have, I can say that if there is an O-Ring there, they are used as seals.
    No tape is needed for those, or for compression connections.

    Many new faucets are coming with their own supplies made to fit 3/8" compression stops.
    This one below fits 1/2" copper (5/8" OD) with a 3/8" compression outlet.

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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    FWIW, in a home, a kitchen faucet is flow restricted, so 3/8" works fine.
  5. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    Now you have easier-to-operate stop valves. So nice upgrade.
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