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Thread: Trap arm slope

  1. #1

    Default Trap arm slope

    I just read in the pipe dope thread that the lav trap arm should have a slight slope towards the trap. How critical is that? I just installed my double sink drains and I had the trap arms slope away from the trap.

    Note that in a different double vanity installed by the builder 18 years ago, the trap arms slope very dramatically away from the trap and we haven't experienced any problems. Thanks.

  2. #2
    Plumber jimbo's Avatar
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    Default

    I don't know why it would slope towards the trap.....that would cause problems.

  3. #3
    Forum Admin, Expert Plumber Terry's Avatar
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    Traps arms should be sloping at a 2% grade "down hill".
    That is the same as 1/4" per foot.

  4. #4
    In the Trades Gary Swart's Avatar
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    Ideally, give it a bit of a slope downward toward the drain. On very short lengths, even level will work OK, but never try to make water run uphill under gravity.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default slope

    IF there were a reason to slope UP from the trap it would be for any piping between the trap and the sink. AFTER the trap the piping slopes downhill.

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