Washer standpipe "height"

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by wilcobravo, Dec 16, 2017.

  1. wilcobravo

    wilcobravo New Member

    Joined:
    Dec 16, 2017
    Location:
    Connecticut
    Hi All -

    I am moving my laundry room, which is currently on the ground floor, directly one floor above, and was planning on just extending the piping vertically (with no horizontal relocation). In looking at the code requirements, there is language about maximum standpipe height above the trap. I'm guessing this is to ensure that the washer can sufficiently pump the waste water into the top of the pipe. I was planning on just running a straight pipe from the floor above to connect with the old standpipe, without a new p-trap on the second floor. Any reason I shouldn't do that? In that case, there would effectively be 8-9' of standpipe height above the trap but the top of the standpipe would be 36" from the floor the washer is sitting on.

    I'm not planning on putting a sink in there, but was planning on running the floor drain (in case of a leak) into that same line.

    Thanks in advance!
     
  2. plumber69

    plumber69 In the Trades

    Joined:
    Jun 20, 2014
    Location:
    Prince Rupert, British Columbia
    I'm confused on your question
     
  3. Sponsor

    Sponsor Paid Advertisement

     
  4. wilcobravo

    wilcobravo New Member

    Joined:
    Dec 16, 2017
    Location:
    Connecticut
    I just want to know whether I can extend the current standpipe up 8 feet to the floor above without putting in a new p-trap.
     
  5. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    NO!!!!!!!!!!!!!!!!! The water's velocity would be so fast that NO water would stay in the trap. You also cannot just "put on another P trap".
     
  6. wilcobravo

    wilcobravo New Member

    Joined:
    Dec 16, 2017
    Location:
    Connecticut
    Thanks - message received ;). Why wouldn't leaving the old one there and just adding a new one work? Also, given that I do need to add a new trap, I was hoping I could somehow use the same trap for both the washer and the floor drain so that I don't need a primer on the floor trap. Any way to do that? Can I put the trap below the floor?

    And will I need a new vent, too, or will the one from the old standpipe suffice?
     
  7. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    The standpipe is 18" t0 30" tall (usually 30"). The trap is roughed in at 6" to 18" above the floor (commonly 12"). (UPC 804.1). 30" + 12" = 42". The trap can be roughed in at up to 18", which gives 48" total height.

    You can't double trap a fixture either.
    Traps are designed to "keep" a water seal, which in turn keeps smell gas from entering your home. It depends on whether you want "home sweet home" or something far more sinister.
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Also note, the trap needs to be vented, and that needs to happen before the waste turns vertical. Your new sink should have its own trap and vent, but the vents can be combined (as can the drain line), but they are individual traps with individual vent lines going up. The vents have rules about how far above the fixtures they must go before they can be combined, and the size of the drain line for the sink and WM need to follow codes as well. An older installation may use 1.5", but today's code requires it to be 2" for the WM, so that could be an issue, too.
     
  9. wilcobravo

    wilcobravo New Member

    Joined:
    Dec 16, 2017
    Location:
    Connecticut
    Alright - here is my new plan: I'm skipping the floor drain into the plumbing (the town inspector said he'd rather see it empty into the garage directly below anyways so that we'll more readily notice if there is a leak). I opened the wall up a bit and it turns out a vertical vent stack is just one stud bay away, so I'm going to add a trap and connect into that, just like the image below. Anything wrong with that plan? The new trap would be 9' higher than the old one. I am not planning on putting a sink in the room as it is a little small.

    https://forum.ih8mud.com/attachments/image-1264289990-jpg.745911/
     
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Basic rules...once a pipe becomes a drain, it cannot remain a vent (a few minor exceptions, but none that span multiple floors). So, assuming that pipe is truly the vent from below, if you drain into it, it is no longer a vent for stuff downstairs...that would need to be revented above where you made it a drain. Will it work, maybe...depends on the size of the pipes, but it would also not pass code inspection.
     
Similar Threads: Washer standpipe
Forum Title Date
Plumbing Forum, Professional & DIY Advice Need advice on best way to create better washer standpipe under utility sink Apr 11, 2020
Plumbing Forum, Professional & DIY Advice Blockage beyond the washer drain standpipe? Dec 24, 2019
Plumbing Forum, Professional & DIY Advice Help with washer standpipe overflow Dec 1, 2019
Plumbing Forum, Professional & DIY Advice Weird problem With the washer standpipe. The adapter is stuffed down it! Nov 2, 2019
Plumbing Forum, Professional & DIY Advice Troubleshooting Main Drainpipe Leakage & Possible Washer Standpipe Design Issue(s) Oct 10, 2019

Share This Page