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  1. #1
    Join Date
    Feb 2008
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    15

    Default Faucet supply compression fittings: how tight?

    I'm trying to install a new kitchen faucet which has unthreaded copper input tubes. How tight should the compression nut fittings be? They're brass fittings with a brass ferrule.

    I tried tightening them hand-tight plus a quarter turn with a wrench, and the supply lines slipped off the tubes under their own weight. I tightened them a little more and they stayed, but they rotated freely around the tube. A little more and they rotate around the tube with some friction when I try to turn them. I tried turning on the water and they dripped a lot.

    Should the fitting not rotate around the tube when it's tight enough? If I just keep tightening a little at a time until there are no leaks, will that be tight enough so they won't leak in the future?

    At the shutoff valve end of the flexible braided PVC supply lines, the 3/8" compression connector has a rubber cone inside. The instructions for the lines said to tighten them hand tight plus a quarter turn.

    But since I had to flex the line to get it to line up at both ends, I had trouble tightening the nut by hand while keeping the first bit of the line straight. I tried to figure out where "hand tight" was by tightening slowly with a wrench, and seeing if I could still loosen the nut by hand after each quarter turn. So I might have gotten it wrong.

    There's a small spray from one of them when I turned on the water. Is it too tight or not tight enough? What are the symptoms of overtightening? Do I have to throw out the line if I overtightened it, or can I just loosen it?

  2. #2
    Join Date
    Aug 2007
    Location
    Denver, CO
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    666

    Default Re: Faucet supply compression fittings: how tight?

    The ferrule should deform the tubing and be pressed into it when itís tight enough.

    Thatís pretty tight.

  3. #3
    Join Date
    Feb 2008
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    15

    Default Re: Faucet supply compression fittings: how tight?

    kentw, I understand that much. But that doesn't help me figure out when I've tightened the nut enough, unless you're suggesting that I loosen the nut all the way and check if the ferrule is pressed into the tubing.

  4. #4
    Join Date
    Aug 2007
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    Denver, CO
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    666

    Default Re: Faucet supply compression fittings: how tight?

    Quote Originally Posted by JimDorp View Post
    kentw, I understand that much. But that doesn't help me figure out when I've tightened the nut enough, unless you're suggesting that I loosen the nut all the way and check if the ferrule is pressed into the tubing.
    Jim, first off I was not making light of your post and hope you did not take it that way. I did a cabin full of these last spring and will tell you I ain't no plumber. I think it would take a lot of torque to over tighten them.

    I used two pairs of channel lock type slip joint pliers. One to hold the valve body and one to tighten the nut and use a fair amount of force to get them seated.

    How much? I donít know how to explain that but you will not have any spin or rotation when they are tight enough.

    Maybe get the first one seated and use the same amount of force on the others.

  5. #5
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,557

    Default Re: Faucet supply compression fittings: how tight?

    Tighten the nut down snug, turn it about Ĺ turn more, slowly turn on the water on, if you have a leak tighten until leak stops. Works for me.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Feb 2008
    Location
    Memphis, not Egypt
    Posts
    183

    Default Re: Faucet supply compression fittings: how tight?

    Try applying a light weight lubricant or no set pipe dope to the ferrule. Pipe dope is not recommended by the manufacturer but is recommended by plumbers. Make sure the supply is nice and square so that you can tighten it to finger tight and then crank it to 3/4 past that if it leaks turn of the water and crankit another 1/4 or 1/2. It will hold or leak or eventually break. If so get more parts and try again. YAY plumbing. I am making light of your frustration because this is minor and basic and not that big a deal so eat some pie and breathe.

  7. #7
    Join Date
    Feb 2008
    Posts
    15

    Default Re: Faucet supply compression fittings: how tight?

    Well, I tightened the connections bit by bit until they stopped leaking. Thanks for your advice.

    Now to fix the very slow leak at the garbage disposal outflow elbow (I think I need a new plastic beveled washer for a slip nut), and the intermittent leak out the stem of the hot water shutoff (the packing nut was stuck and couldn't be tightened, but it stopped for now).

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