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Thread: How to replumb this for disposer?

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  1. #1
    DIY Junior Member Patcs2's Avatar
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    Jan 2009
    Atlanta, GA

    Default How to replumb this for disposer?

    Just bought this house and want to add a disposer under the double kitchen sink. The "flipper" we're buying from moved the sink from across the kitchen and the new one isn't tied into the vent stack. Our home inspector said the nearest vent is seven or eight feet away...inaccessible and too far from the fixture to satisfy code anyway. He suggested we have a air admittance valve put in when we have the disposer installed. The under-the-sink drain plumbing doesn't seem to be well done and needs a makeover when a disposer's installed. I think that's an S trap they created in there.

    Dishwasher's to the left of the picture and the countertop is granite (tougher to cut in an above-counter AAV?) We'd like the disposer under the left side sink.

    I'm not sure I'll attempt this, but whether we have it done by a licensed plumber or I do it, any suggestions on how, done right, it should look? I can post another picture if the "big picture" and "under the hood" views don't show things adequately.

    Thanks for any advice.

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  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Sep 2004
    New England


    Sounds like you may be confusing an air gap (that installs above the counter - well, actually through the counter) and an AAV. If you did use an AAV, it would be as high as possible under the counter where you could still unscrew it to replace. There a lots of diagrams of other projects where this has been done to go by.

    Yes, that does look like an s-trap. Even if it had a loop vent (which would pass code most places), it's still not installed properly.

    The disposal will have a DW inlet port, you can use that. You need a baffle T on the part connecting the two sinks to prevent the outlet of one from flowing to the other sink. The disposal acts like a pump, and without that, you'll have problems.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    Just for starters, everything will have to be redone. The drain outlet is too low to connect a P trap and avoid the S trap like you now have and you must have a vent. Frankly, I think you'll be time and money ahead to hire a plumber to do everything that needs to be done to make this a legal installation.

  4. #4
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    Sometimes I would get asked to look at plumbing that a "flipper" wanted done. My suggestion; don't ever buy a home that has been "flipped".
    They don't so much cut corners, they don't even have corners.

    The kitchen drain in the wall is supposed to be 2". The vent and the trap arm can be 1.5" The vent comes off at the trap arm height. In this case, at least install an AAV inside the cabinet.
    Many places require an Air-Gap for the dishwasher. At least high loop the drain hose before draining to a disposer or a waiting tee.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Aug 2004
    Cave Creek, Arizona


    Does anyone actually think a "flipper" would know HOW to install a proper loop vent? And, if he did, would he actually spend the time and money to do it correctly knowing that once he put the drywall in place no one would ever see it anyway? My gut feeling is that if he knew ANYTHING about proper plumbing, that drain opening would NOT be right at the cabinet floor. And if there is no vent EVERY configuration will be an "S" trap.

  6. #6

    Default A slightly defensive response...

    As a contractor and an occasional "flipper" I have to say I understand your disparaging remarks when I look at the "competition," but it's not always the case. Some of us do know what's what and have other successful businesses in the trades and flip to keep crews busy and make a little money without clients mucking things up . The pressure to get it done does mean you don't always go the extra mile, but professional work is still performed by some of us. It may be few and far between tho...

    Rehabbers do provide a good service (bringing undesirable and undervalued homes up to par) and around these parts have to be licensed contractors (exactly as a developer would) -- though I'd guess that less than 25% are. It still doesn't guarantee much, but it means they have to have and maintain bonding and insurance.

    Obviously it's about the craftsmen involved. I've fired a plumber (that you may know Terry) for drinking a client's alcohol from their liquor cabinet on a remodel job. Several have shown up drunk or high & get sent home. Should I suggest you never hire a plumber without a sobriety and pee test?

    That being said I found this old thread while searching for answers to a similar plumbing question which I'll post separately. Don't flame me too badly!


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