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Thread: Distance between trap and shower drain

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  1. #1

    Default Distance between trap and shower drain

    Installing a center drain shower pan where tub was. Old tub was elevated so trap and drain were above the floor (mobile home). I would rather not cut the floor under the shower to install the trap. Can I run about 25-30" of horizontal drain line (with 1/4"/foot angle) from shower drain and then put the trap in before before connecting to the vertical drain/vent where tub was connected? Also, this will be 2", not the tubs' 1 1/2" line. So, does the trap have to be right under the drain?

    Thanks

  2. #2
    Homeowner geniescience's Avatar
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    Default you can.

    and the consequences are that the piece of horizontal pipe before the P trap will eventually let smells float back up out the drain, as a certain amount of hair, skin cells, soap scum and other organic matter deposited on the bottom of the pipe will biodegrade and smell. I think it's not as serious as sewer gases, which are dangerous.

    david

  3. #3
    DIY Member FJK's Avatar
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    This is a similar question to the issues I have on my 2" drain post on this form.
    Without giving a DIY (me) a bad name, I pose the question..... Could you have a redundant trap? Meaning, put a 2" trap in the shower drain (correct location) & plumb down to the existing 1-1/2" trap, obviously converting from 2" to 1-1/2" along the straight section. The reason I'm asking in my case, getting to the original trap is a pain, due to its restricted location & short stub. Is there a downside to 2 traps in series?

    Thanks, FJK

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    Homeowner geniescience's Avatar
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    no can do. illegal and dangerous. not code.

    it's fine to ask. Sometimes the responses are clear; in a few cases they are a bit dodgy because it is one of the few things that could be debatable, like "best practices" put into code, and not straight out safety issues.

    You also cannot reduce a drain pipe size part way down the line. That will cause blockages.

    david

  5. #5

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    I have a derivative question. We are rerouting the drain from a bathtub in a basement ceiling in my brother-in-law's house. Originally the trap was directly under the tub, which then put the drain about 8 inches or so beneath the joists making a very unsightly intrusion from the ceiling where it then went diagonally about 5 feet to the stack on the other side of the wall. We are thinking of shifting the trap to the end close to the stack, allowing the drain to proceed close to the joists rather than a foot beneath them, perpendicular to the wall and then making a right angle to the stack behind the wall. Would it be okay to have a second, shallower trap directly under the tub to block any smells you mentioned in the answer above? Or alternatively, could one use an "s" trap under the tub, instead of the original "p" one, that would allow the drain to leave then take a right angle directly against the joist?
    Last edited by LaughingCoyote; 05-12-2007 at 08:28 PM.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    If I understand it correctly, an S trap has the inlet and outlet parallel with each other. The arm coming out of the p-trap should be basically horizontal - a bend is okay to get it where you want it. I'll defer to a pro on this, but I think what you want is okay. Just where is the vent, though?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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