How to drain 2 washers into laundry tub drain?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by jpmaddog, Mar 4, 2010.

  1. jpmaddog

    jpmaddog New Member

    Messages:
    4
    Location:
    Pennsylvania
    Our laundry tub drains directly into the slab. Instead of drain two washers into the laundry tub, my wife wants to connect them under the laundry tub and have all 3 go into one p-trap.

    How can this be done?
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,248
    Location:
    Land of Cheese
    The purpose of the laundry tub is to act as a "reservoir" so the water can drain as quickly as the trap and piping allows. Because of the discharge capacity of the 3 combined, it would require each washer to have an individual standpipe and trap draining into a 3" or larger drain.
  3. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    In other words, what you want to do cannot be done, for several reasons. The first reason is that each washing machine AND the tub require their own vented trap. The second reason is that it is highly unlikely the drain piping through and under the slab has the capacity to handle the load. As Cacher stated, the laundry tub serves as a temporary reservoir to hold the high influx of drain water and allow the drain to handle it on a slower discharge basis.
  4. jpmaddog

    jpmaddog New Member

    Messages:
    4
    Location:
    Pennsylvania
    Additional details:
    The drain in the floor is 3" and it's right next to a 4" cast iron pipe that goes straigt up to the roof.

    The new washer needs to handle 4.2 gal/min.

    It all drains well and fast right now. Can't I just tie two standpipes and the laundry tub into one pipe and the have one big trap for it to go through?
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,350
    Location:
    Yakima WA
    No, each standpipe must have its own vented trap.
  6. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,248
    Location:
    Land of Cheese
    Also, if the 4" stack has any other fixtures using it as a drain, the vents would have to be connected at least 6" above the flood rim of the highest fixture draining into that stack.
Similar Threads: drain washers
Forum Title Date
Plumbing Forum, Professional & DIY Advice, Tips & Shower drain washers. May 18, 2005
Plumbing Forum, Professional & DIY Advice, Tips & Extending Dishwasher Drain Hose Wednesday at 10:39 AM
Plumbing Forum, Professional & DIY Advice, Tips & Dishwasher/Disposal drain Sep 16, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Need to move shower drain 0.5 inches Sep 16, 2014
Plumbing Forum, Professional & DIY Advice, Tips & Basement drain (Backwater valve?) Sep 11, 2014

Share This Page