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Thread: P-trap connection

  1. #1

    Default P-trap connection

    Putting in new mud-floor tile shower. After extending sewer line to center of shower, the line will only be about 2 inches below top of slab (not below the slab). My concern is, that to put a new p-trap under new shower drain, I may not be able to connect the p-trap directly to the sewer line. With the shower drain flange resting on slab, the shower drain connection may extend down too low to allow the p-trap to connect directly to the sewer line.

    As long as the top of the shower drain is about 2 inches above the slab and the sewer line is about 2 inches below "top" of slab, can I place the p-trap
    lower and connect to sewer line with short pipe riser and elbow? It seems that only difference is that the p-trap may hold more water than if conncected directly to sewer line.

    Asked question because when I removed the tub, the p-trab was conncected directly to sewer line and all of my sink p-traps are connected directly.

    Also, is it ok to fill in around the sewer line with concrete, in order to fill area in the slab that needs to be cut away.

    Don't think I explained myself well in previous posting and not sure this is ok either. Appreciate your help!

  2. #2
    DIY Senior Member Mike Swearingen's Avatar
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    Default

    Water does not flow (drain) uphill. I'm not a pro plumber, but if I understand what you're wanting to do, it won't work properly.
    All drain lines should slope 1/4" per linear foot toward the main drain, and tie in wherever necessary, or you're going to have water backing up in the shower.
    Plan "B".
    Good Luck!
    Mike

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default trap

    IF you are doing the shower floor the normal way, it will be about 2-3 inches above the slab. The way the "P" trap is constructed it will have plenty of room in the riser to set your drain's flange even with the slab.

  4. #4
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    Default

    Quote Originally Posted by hj
    IF you are doing the shower floor the normal way, it will be about 2-3 inches above the slab. The way the "P" trap is constructed it will have plenty of room in the riser to set your drain's flange even with the slab.
    What kind of normal shower involves locating the drain 2 - 3 inches above the slab?

    I think what he is saying is he wants to raise the discharge of the p-trap to meet the existing pipe. Then it's all downhill from there. As a result, more water will be sitting in the P-trap than it typically would. All connections would be below the slab. No uphill running water.

    Jason

  5. #5

    Default

    Can you draw a picture? As long as no portion of the drain is above the shower flange and there's an average fall of 1/4" per ft from the flange and the downstream side of the trap is below the flange, it should be ok.
    (important note: I'm not a pro)

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