minimum height for laundry standpipe?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by DavidTu, Dec 22, 2010.

  1. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    Under UPC the laundry standpipe p-trap must be: 6" <= floor <= 18"
    Q1: where is the measurement taken from w/ regard to the p-trap? In Peter Hemp's book it shows it as the connection point between the standpipe (above) and the p-trap (as opposed to the weir or dead bottom of the p-trap, to name to other obvious points of reference). Is Hemp's drawing correct?

    Under UPC the laundry standpipe top must be: 18" <= p-trap <= 30"
    Q2: is the aim of these two restrictions to end up with the standpipe at 36"? One interpretation would be that if the p-trap is 6" from floor, standpipe should be 30" from p-trap, and if p-trap is 18" from floor standpipe should be 18" from p-trap... this is NOT what the code says, but is that what it means to say?

    OR to put it another way...
    Q3+: what is the recommended height above the floor for the top of the standpipe? Should it be above the flood level of the washer (as I've seen mentioned in one resource)? Can it be "hidden" behind the machine (for aesthetics) or does it need/want to be above the machine?

    Thanks.
  2. Basement_Lurker

    Basement_Lurker One who lurks

    Messages:
    668
    Location:
    Victoria, BC
    If you search, this has probably already been answered several times by now.

    804.1 All plumbing fixtures or other receptors
    receiving the discharge of indirect waste pipes shall be
    approved for the use proposed and shall be of such
    shape and capacity as to prevent splashing or flooding
    and shall be located where they are readily accessible
    for inspection and cleaning. No standpipe receptor for
    any clothes washer shall extend more than thirty (30)
    inches (762 mm), nor less than eighteen (18) inches
    (457 mm) above its trap. No trap for any clothes
    washer standpipe receptor shall be installed below the
    floor, but shall be roughed in not less than six (6)
    inches (152 mm) and not more than eighteen (18)
    inches (457 mm) above the floor.

    The top of the standpipe MUST be above the FLR of the appliance no matter what, and it sounds like your code wants a minimum dimension of 18", and a maximum dimension of 30", for the standpipe dimension. That's more than enough information to figure out what you have to do.
  3. Redwood

    Redwood Master Plumber

    Messages:
    7,452
    Location:
    Connecticut
    It definitely needs to extend above the water level of the machine or it will gravity drain the machine.
    The discharge on most machines is pumped without a valve.

    A trap set 6" above the floor with an 18" standpipe while legal would be a problem for most machines.
    Last edited: Dec 22, 2010
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,334
    Location:
    Yakima WA
    All of the machines I am familiar with have a control panel on the back that extends above the level of the tub. This would allow the standpipe to extend above the top of the tub and still be hidden. That would put the height somewhere around 36". I hope you know the drain is supposed to be 2" pipe. In years past, 1-1/2" was enough, but new machines empty the water much faster than a 1-1/2" pipe can accommodate.
  5. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    OK thanks, the FLR is the key determinant then for the overall height. Yes I am running 2" pipe. BUT no one has indicated what the point of reference is for the p-trap height to be measured as being 6" above the floor... what part of the p-trap must be > 6" from floor?
  6. Gsalet

    Gsalet George the Plumber

    Messages:
    83
    Location:
    San Francisco
    I believe the code states the trap must be no less than 6" or greater than 18 to the weir of the trap.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,522
    Location:
    Cave Creek, Arizona
    I put the trap somewhere between 6" and 18", and the standpipe at 42". That puts the box at a point where the valves are accessible, in case the homeowner is one of those "three people in America" who acutally turn the valves off after every wash.

    Your "less than/greater than" statements are slightly incorrect. It should be 6" <= P trap <= 18" and 18" <=standpipe <= 30"
    Last edited: Dec 23, 2010
  8. Basement_Lurker

    Basement_Lurker One who lurks

    Messages:
    668
    Location:
    Victoria, BC
    I also put the standpipe/washbox at 42".
  9. jaginc

    jaginc New Member

    Messages:
    1
    Location:
    Oregon
    Thanks for the accurate info.

    I know this thread is a bit old and you may never read this, but thanks so much for actually quoting and referencing the applicable code. I spent several frustrating hours searching various forums and threads, finding lots of statements, but no code references to back them up. I am trying to figure out how to plumb in a washing machine in a daylight basement which is part of a large addition/remodel to my house. Originally the laundry was to be on the other side of the wall on the main level and the plumbing would have been easy, but we decided to move the laundry to the basement part way through the project. Unfortunately we are a few inches too low to put the trap in the wall easily. At least now that I am able to find the exact requirement in the 2011 Oregon Plumbing specialty code, I know the exact limitations I have to work around.

  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,522
    Location:
    Cave Creek, Arizona
    quote; I know this thread is a bit old

    I was wondering why every posting prior to yours was dated 2010, and yours was "yesterday". I thought maybe the website was broken and misdating the posts.
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