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So, some background on this issue first... our old dishwasher seemed to work fine when we first moved into this house, but within the last year it started having a drainage issue. Water would be left standing in the bottom of the dishwasher after the cycle finished which was leading to yucky stuff down there as well. My husband pulled the dishwasher out, unplugged the drain hose, made sure the trap was clean, etc. Unfortunately, the problem was not solved.

Finally, we just got a brand new dishwasher hoping that our drainage problem was behind us, but sadly the new dishwasher doesn't drain either! HELP! All that I can see is a black drain hose which goes down into our crawl space and then back up and attaches to our sink. The sink has not had any drainage problems. Any ideas?

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What happens if you put water into the drain pipe without the dishwasher installed. Does it drain? – Joe Philllips Feb 17 '11 at 18:28

You say that the drain hose runs down to the crawlspace then back up again. It's winter time (at least in the northern hemisphere); I wonder if the water is freezing in the drain hose at the lowest point, enough that hot water from the dishwasher isn't able to reach it to melt it (there would likely be a layer of cold liquid water between the dishwasher and the bottom of the hose).

I think it's odd that the drain hose feeds through the crawlspace; any installations that I can remember seeing have a hose feeding through the cabinet wall to the sink's plumbing. Is the dishwasher adjacent to the sink so that you could redirect the hose like that?

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good point... if it is freezing the line up manually put some very hot water in the dishwasher and that should help to un-freeze the line. – boxed-dinners Feb 17 '11 at 20:09
@boxed-dinners - unless the water flows through, the ice will not melt and dishwashers usually have HOT water in them anyway. – Mark Schultheiss Feb 17 '11 at 23:42
yes, however the volume of hot water could shut down the dishwasher because it was backing up so quickly and then when you opened the dishwasher and saw lots of water it wouldn't have time to melt before the water was removed. – boxed-dinners Feb 18 '11 at 13:39

Your drain line could be clogged.

The flexible drain hoses tend to collect grease over time, and will eventually cause the hose to become completely blocked. If you disconnect the drain hose, you should be able to blow into the hose to see if it is clear. If not, you can either manually clean it out, or get a new flexible hose. If you decide to replace it, you might want to consider getting a clear hose. This way, you can see if there is any buildup or obstructions in the hose without having to disconnect the line.

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The problem may be in the dishwasher itself. If you don't pre-rinse most of the stuff off your pot/pans/plates etc. that food gets washed down the drain. However sometimes it log-jams itself inside the dishwasher. This has happened to me in the past.

Take out the dish-racks in the washer and manually clean everything, you'll probably come up with more junk than you would think.

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Since the drain hose is flexible, it may be kinked - see of you see smooth curves, no sharp bends - it may be restricted at any sharp bend.

See if you can connect some kind of container to the hose end such as an old soda bottle (cut off like a funnel) or an actual funnel. Hold the end up above the rest of the hose. Pour water in - it should flow freely and fairly quickly down. If it does not, you have a restriction somewhere, try to isolate that.

Check the hose by removing it - take it somewhere (outside?) where you can repeat the process to see if water comes out the other end - if not, a hose is a cheap purchase. If it does flow freely, and did not when connected you have a restriction somewhere further along the drainage system.

You can also test the dishwasher pump by attaching the hose to that, then putting the end in the sick (loose) and see if water comes out. (watch for kinks/sharp bends and avoid those).

If those both fail, you have a restriction somewhere else.

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