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Long story short, I renovated my kitchen and have two counters. I have a counter where the oven and kitchen sink reside. Across from the counter (about 5 ft), I have a dishwasher across. I have a drainage tube (rubber hose) that runs from the dishwasher to the sink (about ~8-9ft long). Whenever I try to drain, the water just stays there and does not drain. My setup

Actual pic (with dishwasher taken out for troubleshooting)

I took out the drainage hose and was able to drain the water in the dish washer in a bucket (through the dishwasher's drain cycle). When I bought the dishwasher, I was assured that the pump was strong enough to pump the water and the drainage pump will continue to pump as long as there is water in the dishwasher. I think the dishwasher is not draining due to the distance that the water has to travel to drain (I checked for clogs, there are none). I am guessing I messed up big time and may need to custom fit my dishwasher with a much stronger pump? I'd greatly appreciate any advice or words of wisdom.

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I don't understand how your discharge will run from counter to counter. You have a hose going across your kitchen? –  DMoore Aug 31 '13 at 5:43
    
Could the answers include something about air gaps? Would adding an air gap help the flow (by gravity) from the dishwasher? –  Pigrew Aug 31 '13 at 5:58
    
Sorry, if I was being vague. I have a rubber hose that goes is around the wall. Basically, in this pic i.imgur.com/FML4n.jpg ...the rubber hose goes behind the stove, into the wall and into the dishwasher. –  DavidW Aug 31 '13 at 20:52
    
does the installation manual specify a maximum run length for the discharge hose? How about a maximum height differential for the discharge hose? If you're not exceeding these, check for kinks in the hose, or consider a larger diameter hose, which would be less restrictive. –  mac Sep 30 '13 at 13:55
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4 Answers

I can only think of three options here...

Water flows downhill

The first (less optimal) option, is to raise the discharge up and allow it to flow down to the drain connection. In this scenario, you'll want to have the discharge tube go up to an air admittance device (AAV) or air gap. From there it should flow downhill (1/4" per foot), until it reaches the garburator connection.

Option 1

Use a separate drain

The other option, is to discharge the dishwasher to its own drain. Install a properly vented standpipe near the dishwasher, and connect the discharge tubing to that (follow local plumbing codes).

Option 2

Go under the floor

The last option is to run a drain line under the floor, and attach to the sink drain below the floor. Install a trap near the dishwasher, and run a proper drain that tees into the sink drain (follow local plumbing codes).

Option 3

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@DavidW: The first solution is the most universal. The high point of the line being close to the dishwasher is very important. –  wallyk Feb 28 at 5:08
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With a long discharge run, the height is important. As the water is discharged uphill (which it is), there is water in the line. When the dishwasher stops the discharge cycle the water in the pipe drains back into the dishwasher. The size of the pool of water depends on the length of the discharge pipe and "the diameter of that pipe". There is not much you can do about this since the outlet of the dishwasher and inlet of the trap you tie into are at some height and you can't change that. You can only minimize the pipe length.

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I actually don't think I can shorten the length of the drainage hose (which goes behind the stove, into the wall and into the dishwasher which is across). I was wondering if I could make the pump more powerful or add another pump along the way to make it discharge. –  DavidW Aug 31 '13 at 20:55
    
I wonder if you could add a p-trap at the outlet of the dishwasher? I have never seen this but if you could provide for air relief at the dishwasher p-trap (which should be higher than the entrance to the disposal), with a check valve on the air releif so water doesn't blow out under the cabinet, then the amount of water available to drain back into the dishwasher would be minimal. What I am not sure of is the air relief constructed in this way (i.e., not leaving the cabinet). This also means water would always be in the drain line in the wall. –  Richard Raustad Sep 3 '13 at 15:05
    
if the entire water volume of the discharge hose drains back into the dishwasher, could a check valve be installed near the dishwasher to prevent this from happening? –  mac Sep 30 '13 at 13:56
    
@mac The problem with a check valve is that the next time the dishwasher drains, it has to push not only the water being discharged, but also all the water still in the drain line. –  Tester101 Sep 30 '13 at 15:00
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@Tester101 Yup, but as long as the "head" doesn't exceed a "normal" installation, it should be OK, right? The amount of water lifted would be the same as if the dishwasher was right next to the sink. –  mac Sep 30 '13 at 15:36
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Its not canon that the dishwasher drains to a garbage disposer, its just usually more convienient.

I would try to go down, through a vertical p-trap, to a connection below. As Pigrew notes, some method of back filling the hose with air as it drains, (break the suction and keeps the traps from being siphoned) either a hose loop to the top of the cabinet space or an air admittance valve enter image description here

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In that image, the "p-trap" isn't considered a p-trap. p-traps must have a vent before the pipe turns downwards (there are length limits, too). –  Pigrew Aug 31 '13 at 14:20
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On top of the other solutions, there is a way to to use a booster pump with a flow switch. This would allow you to rum the piping any way necessary, and not have to worry about slope of any kind. Found this as an example. Flow Switch. Then all you would need is any 120V pump. There are also certain pumps available on the market that have flow switches build into them.

The downside to this, besides the added cost, is that power must now be run and the pump will take up cabinet space.

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