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  1. #1
    Join Date
    Apr 2009
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    2

    Default dishwasher drain line

    I am getting a new dishwasher and need to isntall it myself as the delivery people said they cannot install it because I do not have an air gap? On my current dishwasher the drain line goes through the floor under the house and attaches directly to the drain line. I was having some issues with my dishwasher leaving soap residue on the dishes and an installer said the drain line with no air gap is the problem. How do I correct this? People cannot believe I do not have a garbage disposal so they seem perplexed on how to install the air gap or even if I really need one???????
    HELP!

  2. #2
    Join Date
    Mar 2009
    Location
    OKC
    Posts
    247

    Default Re: dishwasher drain line

    I'm not positive but i think there are diswashers available that already have an air gap, or don't require one.

  3. #3
    Join Date
    Oct 2007
    Posts
    175

    Default Re: dishwasher drain line

    The air-gap is just a vent for the drain line - it prevents siphoning and backflow - it's not going to clean you dishes any better with or without it.

  4. #4
    Join Date
    May 2008
    Location
    Pacific Northwet
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    1,627

    Default Re: dishwasher drain line

    The air gap is typically an ugly little chrome dome that pokes through top of the counter or sink. (If you have an unused hole on your sink -- this is the place for it.) The drain line from the dishwasher hooks to the air gap underneath the counter. From the air gap, another hose connects to a "dishwasher tee" that is on the sink's drain line between the strainer basket and the trap.

    The folks at any small hardware store or plumbing supply shop should be able to illustrate this to you, since they'll have all the parts right there. The big box will have the parts too, but if they ask "what's an air gap?" or they send you somewhere other than the plumbing department, that's your cue to get away quick before the stupidity rubs off on you.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  5. #5
    Join Date
    Apr 2009
    Posts
    2

    Default Re: dishwasher drain line

    Thanks so much - that is very helpful. I may have to remove my spray hose or cut another hole for the air gap thing. Is there some kind of code that tells you how high the drain line has to be in relationship to the water line coming in to the dishwasher?
    Right now my water line comes up from the floor and the drain line connects under the floor so it is a few feet lower than my sink drain line and lower than the water connection for the dishwasher.
    Thanks for all your help!

  6. #6
    Join Date
    Dec 2008
    Location
    Midwest
    Posts
    173

    Default Re: dishwasher drain line

    Since a dishwasher has potable water and connects to the sewer line it is recommended top have one. Just take the drain hose and run it up to the bottom of counter top and secure. I use a zip tie and connect to the siink clips. Then run hose to where ever you need. Most newer dish washer have a check valve at drain connection any way. Or you can get a dishwasher tail piece.

  7. #7
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,627

    Default Re: dishwasher drain line

    One thing that surprises me is that residential dishwashers aren't required to have an atmospheric vacuum breaker or double check valve on the water supply line (I think they are required in commercial kitchens). While the drain air gap prevents soiled water from backflowing into the dishwasher, it won't prevent soiled water that's still in the dishwasher from backflowing into the potable water line. I suppose the solenoid valve may provide some backflow prevention, but is it adequate?
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  8. #8
    Join Date
    Oct 2007
    Posts
    175

    Default Re: dishwasher drain line

    Your water supply line is at 40-50psi the waste line is essentially ambient.

  9. #9
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,627

    Default Re: dishwasher drain line

    Quote Originally Posted by libcarp View Post
    Your water supply line is at 40-50psi the waste line is essentially ambient.
    True, and the pressure would prevent backflow. That much is obvious. But I'm talking in the event that there is a loss of pressure or even a vacuum on the supply line, which can happen if a pipe breaks below the level of the DW. That could allow contaminated water back into the potable water supply.

    Where I live, backflow prevention is required on irrigation systems connected to the city water supply.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  10. #10
    Join Date
    Aug 2007
    Posts
    612

    Default Re: dishwasher drain line

    The water supply on our dishwasher is on the left side about halfway between the lower and upper rack. The dirty water level never gets near that high to be sucked back into the supply line, it only gets about 3 or 4 inches deep in the bottom of the dishwasher.

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