vertical distance to p-trap for washing machine

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by sam., Jul 3, 2011.

  1. sam.

    sam. New Member

    Messages:
    4
    Location:
    Brooklyn
    Hey, I am new here, prior just reading and learning. I am Sam, for Samantha inspired by "Bewitched" ( tv show from 60-70s ).

    Due to tight quarters my washing machine drain empty's into the 3' stand on the floor and then 4' additional from the basement ceiling till it hits the p-trap. This was so I could vent it properly. It is an old house and this was the best way to catch the vent (8" above top of p-trap ) without destroying a wall that is full of lath, plaster, sheet rock... nasty mess. Is that ok?

    Thanks,

    Sam
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Probably not. I assume the NYC code is probably as strict as the UPC which requires the following:
    Trap shall NOT be below the floor.
    Trap shall be 6 to 18 inches above floor
    Standpipe SHALL be min 18" max 30"
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,797
    Location:
    Cave Creek, Arizona
    quote; this was the best way to catch the vent (8" above top of p-trap )

    The standpipe is much too long, because it allows the water to gain a high velocity before it reaches the trap. And, I am not sure what the significance of "8 inches above top of P-trap" is because there is no regulation like that.
  4. sam.

    sam. New Member

    Messages:
    4
    Location:
    Brooklyn
    "high velocity"

    thanks HJ, jimbo, what does the high velocity cause? I had a feeling it was wrong.

    I just need to wash the clothes until my good plumber comes back from VK end of July. I then can dig out the wall and bring the vent connection in high enough to correct the trap. The trap was originally installed below the floor with no vent.

    So if I understand correctly, there is no regulation on the vertical distance from p-trap to vent?

    Sam.
  5. Terry

    Terry Administrator Staff Member

    Messages:
    15,110
    Location:
    Bothell, Washington
    The vent comes off at the same level as the trap arm.

    Otherwise it becomes and S trap and it siphons.

    Like mentioned above, too long of a standpipe and it can also siphon a trap
    Too short of a standpipe and it can overflow.

    The vent is between the p-trap and the connection to the other plumbing.
    It breaks the siphon, otherwise you trap gets sucked dry and whatever is downstream of that, you will get to smell in you home.
    Vents go through the roof and daylight in the breeze and get dispersed outside of the home.
    If you look on the roof, you will see pipes penetrating the roof.
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