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Thread: Loop for Dishwasher Drain Pipe

  1. #1

    Default Loop for Dishwasher Drain Pipe

    We had a new dishwasher put on last summer. No problems until this summer when we had new countertops and new undermount sink etc. We used this opportunity to purchase a new Sinkerator Premium 3/4 hp disposal or whatever the model was called.

    A day or two after they finished, I noticed that the dishwasher had water in it. So I looked up the problem in the internet and this site and learned about the loop etc. We don't have an air gap. I've attached a pic. Will simply looping the pipe up solve the water backing up issue? Thx in advance for your thoughts.
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  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    You need to run the hose up to under the couter as high as you can go. The way it is, any clog will put crud from the sink into the DW, a very unhealthy situation. Depending on where you live, you may be required to install an air-gap. If you had one, that situation would be essentially impossible.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Jack of all trades frenchie's Avatar
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    You have enough slack on that line for a raised loop. Attach it to the underside of the counter with a clamp. That'll solve your problem.




    ...Is it me, or are a lot of this weekend's questions about fixing work done by hacks?

  4. #4

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    Did you knock out the dishwahser plug?

  5. #5

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    The sad thing is that the granite counters and cabinets were done by a very reputable company. They do the faucet and disposal hookups and part of the service (and would've addressed had I said something) but clearly this why a licensed plumber always get hired when we need work done in the house.

    Quote Originally Posted by frenchie
    ...Is it me, or are a lot of this weekend's questions about fixing work done by hacks?

    Oh yeah, our code doesn't require air gaps. Never had this problem before this, but I presume the loop will be an easy & quick solution.
    Depending on where you live, you may be required to install an air-gap.
    ??? I will have to look up what that is.
    Quote Originally Posted by palmstate
    Did you knock out the dishwahser plug?
    Last edited by lpennington; 08-05-2007 at 03:22 PM.

  6. #6

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    Where the dishwasher hose connects to the disposal. There is a plastic plug in there incase you don't have a dishwasher attatched.

  7. #7

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    I don't think so. If I plug the sink, then fill it with soapy water, you see some of the water go thru the disposal and into dishwasher hose so there's nothing plugging the water from the disposal ... if that makes any sense.
    Quote Originally Posted by palmstate
    Where the dishwasher hose connects to the disposal. There is a plastic plug in there incase you don't have a dishwasher attatched.

  8. #8
    Master Plumber Dunbar Plumbing's Avatar
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    Quote Originally Posted by lpennington
    We had a new dishwasher

    A day or two after they finished, I noticed that the dishwasher had water in it. So I looked up the problem in the internet and this site and learned about the loop etc. We don't have an air gap. I've attached a pic. Will simply looping the pipe up solve the water backing up issue? Thx in advance for your thoughts.
    It's a cross-connection between a device for sterile utensils and your bacteria-laden waste pipe.

    High looping is still a direct connection to the waste system, once momentum starts to roll, it's the same as a garden hose siphoning water over top the edge of a pool.


    Oh yeah, our code doesn't require air gaps. Never had this problem before this, but I presume the loop will be an easy & quick solution.
    Quick and easy?

    The licensed plumbing contractor for lowes in my area is going to feel my wrath come monday afternoon when his nonsense of not installing the new dishwasher to code, which involves an Air Gap. He blatantly lied to the customer stating they didn't need it because there is a check valve thingy that is built into the dishwasher. An Air Gap offers the best level of protection in all backflow situations and has no moving parts to wear out and fail. It uses the free atmosphere to protect.

    That check valve thingy is is a mechanical device that can and will fail. The dishwasher was installed in Kentucky so my two trips totalling $85/hour to correct their ignorance is going to make sure they install plumbing to code.

    Telling them doesn't work; hitting their back pocket along with an irate customer who won't hesitate to turn them into the BBB or AL has a good way of fixing stupidity.

    That installation above looks like a shoddy install. That doesn't even look like a continous waste tee; end outlet tees don't have a bottom nut......the pipe connecting to it will though. It looks like a center outlet tee turns sideways with the baffle cut out. ALSO, that gray PEX line heading to the dishwasher; better replace that soon because those are notorious for leaking at the connections due to the vibration of the dishwasher. GOOD LUCK

    No wander you're on here with plumbing problems!!!!
    Last edited by Dunbar Plumbing; 08-05-2007 at 04:18 PM.
    Read what the end of this sentence means.

  9. #9
    Jack of all trades frenchie's Avatar
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    Palm, how would he be getting water in the dishwasher if the plug wasn't out?

    Pennington - ignore Palm, he obviously didn't read your post.

    In jurisdictions where an air gap isn't require, a high loop is still needed - it's in the dishwasher installation instructions, and the hanging bracket for the hose usually come with the DW. Just raise a section of hose between the two, you'll be fine.



    Edit: Rugged - really? All the DWs I've ever seen put in, here, just had a high loop. Never a problem. Did my plumber set up a bunch of illness traps? You're scaring me...

  10. #10
    Licensed Grump GrumpyPlumber's Avatar
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    Lift the flexible hose from the dishwashers drain...clip it up as high as you can...problem solved.
    The sinks drain is backing into it.
    "The biggest regrets we have in life are the chances we never took."

  11. #11
    Master Plumber Dunbar Plumbing's Avatar
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    Quote Originally Posted by frenchie


    Edit: Rugged - really? All the DWs I've ever seen put in, here, just had a high loop. Never a problem. Did my plumber set up a bunch of illness traps? You're scaring me...

    I tell you this logic straight from being a master plumber and a licensed backflow tester in my state: YES

    Whether that code is laxed from state to state, whether your brother from minnesota or your aunt claude from michigan has had a dishwasher with no air gap for 40 years,

    that drain line is directly connected to the dishwasher.

    Why else was this thread started.....along with the 1000's I see across many plumbing forum boards. It's a direct connection and the high-looping only increases the odds of it not happening, not preventing.


    Here's one for the non-believers:

    When you have a clogged kitchen sink and you start to plunger those drains, where does the waste water go?

    Dishwasher.

    I'm vocal on this subject matter because there are those who will never reply to this thread that understand the logic behind the necessity to protect.

    Did you know that every commercial dishtank machine at a restaurant that creates sterile eating utensils must have an Air Gap is code in all 50 states and maybe mexico?

    Why it relaxes on the residential side of plumbing I'll never know, but I've convinced people in non-code areas of the seriousness of the issue, most people that have families are the first to commit when I spell out the dangers. Others like to take chances.
    Read what the end of this sentence means.

  12. #12

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    Quote Originally Posted by RUGGED
    No wander you're on here with plumbing problems!!!!
    Not sure WTF that meant ... I didn't do this myself (I just observe and ask). I do appreciate your insight and even your tone as now I've been spurred to just have our normal plumbing company take care of this.

  13. #13
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    I just went through this new dishwasher, new sink, new countertop exercise, and all the pro parties involved and the county plumbing inspector said all they require is a high loop, so that's what I've got.

    Having said that, Rugged has made a believer out of me. My questions (finally) are: how big a hole do I need in the countertop, is there any requirement to position it in any particular place, and what kind of horizontal clearances do I need below to install one of these things? It's pretty tight under there.

    A few minutes with my buddy Google and I've answered those questions. I also found air gap units priced from $3.99 to $35. Any recommendations? What makes the $35 one more "deluxe"?
    Last edited by Mikey; 08-05-2007 at 05:06 PM.

  14. #14

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    I ended up looping the dishwasher hose from directly where it exits the disposal into an upside-down "U" for approx 10 inches and then it goes down into the dishwasher.

    I filled the sink with soapy water and then drained it with the disposal on and no water made it up and around the "U". I'll let you know what our plumbers say (a Lowes installer coincidentally installed this dishwasher!).

  15. #15
    Licensed Grump GrumpyPlumber's Avatar
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    Rugged's right, but not code here...we simply clip 'em up.
    As for backflow...our code only allows "listed" MFG's to be installed...thats where the state deals with MFG's..us wee folks just do what we're told...I'd assume "listed" DW's here are installed with backflow inside.
    What I saw on this thread was obvious as soon as I saw the pic.
    If you were to go into discussion regarding this topic here in my state with other plumbers...you might get some odd looks....seems every state has it's own list of taboo's.
    For example...here we are VERY astringent on anti-tips...from the sounds of it, other states are more lax.
    There are dozens upon dozens of other examples, like air chambers, drip tee's, PEX/CPVC/Galvy water pipe, and TONS more.
    I don't take it personal when I mention something that is considered very important here and another plumber elsewhere thinks it's silly.
    Yet again another good reason to check LOCAL code when inquiring online...codes are set for local reasons, like water mineral content...local gas pressure / chemical consistancy, weather conditions...etc.
    "The biggest regrets we have in life are the chances we never took."

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