Dishwasher away from sink

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Hillel, Feb 4, 2009.

  1. Hillel

    Hillel New Member

    Messages:
    32
    Location:
    Cleveland, OH
    Hello all,

    Well, thanks in part to this forum, I have proven to be so handy that the wife has a new challenge. She wants to know how possible it is to install a second dishwasher on a wall away from where the sink is.

    Now, it happens that the electrical conduits to run a new circuit are right below that part of the wall, so that should not be a problem.

    The big issue is the where the drain can go. The kitchen sink actually has a long nearly horizontal run (minimum pitch) under the basement ceiling to join the main sewer line just below where this dishwasher would go. [Our sewer line leaves the house just below grade instead of going vertically down into the basement floor.] Would it be OK to put a separate p-trap in the basement and connect with a wye into the end of the sink run where it joins the sewer line? Does there have to be a separate vent for the dishwasher if it still drains into the end of the sink line before the sewer?

    Thanks.
    ---Hillel
  2. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    Yes to both questions. You also need to make the hose accessable to where it connects to the p-trap. In other words , DON"T close the p-trap in the ceiling below under drywall
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    Well, I think it may depend on where you live...many places require an air gap when connecting a dishwasher. With the DW drain located down there, just the other DW running, there might be enough pressure to backflow into the second DW and almost certainly would if there was a clog somewhere downstream. Nothing tastier than what might be clean dishes now covered with dirty drain water from upstream.

    Is there any way you could install a drain, trap, vent and air gap? This would not only be safe, but legal anywhere, if I've got my understanding of things correct.
  4. Hillel

    Hillel New Member

    Messages:
    32
    Location:
    Cleveland, OH
    I don't think we need an air gap here for code. At least, my current dishwasher that is next to the sink does not have one, nor did the one before it from the previous owner, and both were professionally installed. I don't think it is possible to add a vent up along the wall where this would be. I could at least add an extra check valve before or after the p-trap.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,824
    Location:
    New England
    I think this is a mistake...but I'm not a pro. High looping will give you some protection, but you are going to have two different devices that have pumps that can pressurize that drain line. Gravity is one thing, but pumps can push water places where you don't want it. The last thing you want is dishes you think are clean that aren't.
  6. krow

    krow Plumber

    Messages:
    906
    Location:
    Ontario, Canada
    If you do your loops properly on both DW's, the worst that can happen, it may back up into the sink from either DW.
    In my area , we do not require an air gap by code, nor do the clients want to see this contraption on their granite countertops. But we do have to implament the high loop. The only problem with this high loop system is, you get "Joe Handyman Hack" deciding that you don't need a high loop, let alone an air gap, and start stretching the drain hose its whole entirety under the floor.
  7. gardner

    gardner DIY Senior Member

    Messages:
    217
    Location:
    Ontario
    non-professional opinion and conjecture

    I think there's a difference between a "air-gap" fitting that mounts on the counter top, the type of air gap offered by a traditional tailpiece dishwasher nipple, and what someone *might* do by hard plumbing the DW drain into a stand-pipe.

    Even though you may not elect to use a counter top air gap fitting, you still have to make sure that the point where your DW drain joins the standpipe is open to the atmosphere.
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