floor drain and washer sharing trap?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by steverino, Apr 10, 2009.

  1. steverino

    steverino New Member

    Messages:
    9
    Hi,

    Am building a new laundry room in California.
    I really want to protect against overflows, so in addition to auto shut off valves for the washer supplies I am including a floor drain.

    I've read about trap primers and their use, and I also sense that folks don't like them. Those that feed from potable water waste that water, and that's a real problem in Calif right now.

    Can't a washer and floor drain share the same trap so that using the washer will keep the trap full? Can such a drain be plumbed so that the washer pump out will not spill out the floor drain?

    Thanks,
    Steve
  2. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,347
    Location:
    Cincinnati OH
    You can do what is called an inderect where the discharge from the washer
    is discharged above the trap of the floor drain.
  3. Terry

    Terry Administrator Staff Member

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    15,121
    Location:
    Bothell, Washington
    The p-trap for the washer must be above the floor level, and it must have a standpipe.

    You can add a fitting on the standpipe the lets a bit of water flow down to the floor drain p-trap to act as a trap primer.
  4. steverino

    steverino New Member

    Messages:
    9
    Thanks for the reply. I remember seeing that setup in restaurant kitchens in my earlier days.

    I'll do it that way if that is what is needed. If you don't mind a followup question...Is the indirect setup any different than piping the washer outlet into the line just upstream of where the floor drain enters its trap? I had asked about it overpowering the trap, but if that is going to overpower in this setup, then would it also overpower in the indirect setup?

    Thanks again.

    Steve
  5. steverino

    steverino New Member

    Messages:
    9
    Okay. It doesn't need to be accessible, though, right?
    Okay. Thanks! That'd be good, but my naive guess is that I'd have a problem with lint filling that fitting and eliminating the priming. Sorry -- I've never had a trap primer in my hands to look at.

    Steve
  6. Terry

    Terry Administrator Staff Member

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    15,121
    Location:
    Bothell, Washington
    Commercial kitchens will have floor sink that takes the drainage from a food prep sink.
    But that isn't a washer. A washer had a problem with suds.
    Dumping a washer into a floor drain, you would have suds all over the floor.
  7. cwhyu2

    cwhyu2 Consultant

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    Location:
    Cincinnati OH
    I was working on a drawing,but my program is not working properly.
    Like Terry said you do need a stand pipe,min 2" and if you floor drain is 3" you
    should not have a problem.
  8. steverino

    steverino New Member

    Messages:
    9
    My floor drain is just 2".

    I have some rework to do. (Yeah, I know. If I'd hired someone it'd be done correctly by now!)

    So, it seems the only option is the following?
    Washer 2" standpipe into non accessible P trap.
    P trap into 2" vertical vent line.
    Below the floor, the vertical vent line into drain line just downstream of the floor drain trap.
    There is no other venting in the immediate area.

    Trap will remain full due to trap primer sourced by a fitting in the standpipe above (?) the P trap.

    All good? Ugh. I think the floor drain's trap is going to get siphoned dry by the washer draining.

    Steve
    Last edited: Apr 10, 2009
  9. Redwood

    Redwood Master Plumber

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    Location:
    Connecticut
    If the floor drain is not vented it could very easily get its trap siphoned by the washer...

    If the washer and the floor drain share the same 2" line with out increasing to 3 before where the floor drain ties in I see big problems....:eek:
  10. hj

    hj Moderator & Master Plumber Staff Member

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    Cave Creek, Arizona
    trap primer

    A pressure operated trap primer, as opposed to a flow operated one, only dribbles a very small amount of water into the trap every time the pressure fluctuates due to fixture use, so it does not really "waste" water. Or more to the point, you probably waste more water than that when you use your toothbrush.
  11. steverino

    steverino New Member

    Messages:
    9
    I'm not sure where the big problems would arise. If the washer needs a 2" drain, then a 2" drain should be sufficient for that entire line. There's nothing else draining into that line except the floor drain, and the only source of water for that floor drain is the washer.

    Steve
  12. steverino

    steverino New Member

    Messages:
    9
    Nice. I'll research more.

    Thanks!
  13. Redwood

    Redwood Master Plumber

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    Location:
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    The problem would be that any slight restriction in the line could cause an eruption from the floor drain.:eek:
    Last edited: Apr 13, 2009
  14. Terry

    Terry Administrator Staff Member

    Messages:
    15,121
    Location:
    Bothell, Washington
    I did some service work in the crawlspace of one house, that everytime the washer ran, soap suds would come out from under the toilet.

    I went underneath, and fixed some bad slope on some 3" waste.
    That seemed to fix it.

    Imagine a floor drain.
  15. steverino

    steverino New Member

    Messages:
    9
    Thanks, all, for the great input you've offered. I'm working a bit too much in the dark on this one, so I'm arranging a consulting session with a local plumber. I'll count on him to provide a design to follow. He'll also check my other work. :)

    One last question, though...

    Terry mentioned priming the floor drain trap with a takeoff from the standpipe. I really like that idea, but have one concern that you guys might help with. How much of a concern is it that the primer source fixture will cause a lint blockage in the standpipe?

    Steve
  16. steverino

    steverino New Member

    Messages:
    9
    At least it was soap suds! :)
  17. Redwood

    Redwood Master Plumber

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    Location:
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    I have seen a few that weren't...:eek:
  18. piper2

    piper2 New Member

    Messages:
    8
    Floor drain venting

    I have a question about the best way to vent a floor drain I tied in below the WC wye under slab. Do i add a sant. tee above the trap and continue up to roof or do i vent off of floor drain horizontal branch close to 3" main drain and route back to vent for lavatory? My inspector wants a vent or to move wye above wc wye. Any sugesstions?
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