Why is this not acceptable?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by karsc01, Jul 7, 2006.

  1. karsc01

    karsc01 New Member

    Jun 27, 2006
    I've read several posts on here that talked about how having two floor drains on the same trap is not acceptable as shown in the diagram below.
    Could someone explain to me why this is not acceptable?
    I ask because these drains are going to be rarely if ever used and there's no wall or convenient place to bring up the vent on the second one like there is the first (unless I wet vent it from where the first drain is vented over to the second). They're only about 5 feet apart. Does anyone know the main reason the below diagram is not ok? Thanks.
    Last edited: Jul 7, 2006
  2. geniescience

    geniescience Homeowner

    Nov 27, 2005
    humid summers hot, humid winters cold
    Good point!

    Wow! I agree with your line of questioning. I would like to know too.

    I have three floor drains that I just installed. Venting is far more than 5' away on one of them. So, in the "worst" case you will have two drains with two P-traps and drain pines and the venting is far away from the P trap in one case. Not significant.

    At least you have a trap primer. Believe it or not, a Master Plumber told me on Day 1 that he wouldn't bother with trap primers. Go figure.

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  4. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    I don't know why you wouldn't wye off before the vent, and have two vents that tie together and use two p-traps.

    They make trap primer splitters that allow one primer able to feed more than one trap.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    1. As drawn you have a running trap which would not be acceptable in most jursidictions because the trap seal is not visible, (a requirement for almost all traps except for a bathtub).

    2. Using the two traps would allow air circulation between them and once the pipe accumulated a buildup and it became "foul" the odor would be carried into the room. This is a common occurance in kitchen sinks where there is usually only one trap for the two drains.
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