dishwasher filling with dirty water from sink ... help?

Garbage disposal works fine, dishwasher wash/rinse seem to work fine, dishwasher does drain fine after a wash cycle-- only fills up with nasty water (that becomes stagnant and mildewy) after the sink has been used several times/for a long time, such as when i do a large load of dishes by hand... never realize it's happening til a.) i open the dishwasher and "EWW!" or b.) the dishwasher begins to leak/overflow onto floor. yuck :P **note: if the washer is full of water, i simply have to turn on its "Drain" function... the cycle runs and the water is gone... til next time it accumulates. going to try all suggestions! :)

Public Comments

1. Look under the cupboard where the dishwasher drain hose connects to the disposer. From there, the hose should be looped upwards towards the dishwasher. It should go as high as possible to prevent this from happening.
2. It could be that your drain trap is partiality clogged up and when you drain your sink it flows into the drain hose for the dishwasher, Or the hose may just need to be raised up a little higher if it hangs below the U trap. The dishwasher uses a pump to drain the water so it doesn't matter if you raise it up Remove the U trap and clean it out. It will be nasty so wear gloves.
3. A second cause could be that your backcheck valve could have worn out. It's basically a one way rubber diaphragm in the pipe that keeps the water draining out the right direction when there are several drains connected. The rubber wears out after a while from the soap and fats that soften it. If handling something like this is too yucky for you, call a plumber.
4. The Uniform Building Code (in Wisconsin) requires an air break in the dishwasher discharge hose. But I admit in my house I didn't want the air break above the counter. So I did what your first 2 answers suggested. I have my discharge hose clamped (a pipe clamp - looks like a "C" with a wing on one side for a screw) to the underside of my counter top with a SHORT screw. It isn't strictly code but it accomplishes the same thing. Sometimes looks are more important.
5. Hose to drain should be higher than where it is connected. Loop it up and tape. One other thing is your sink drain could be partually plugged Forcing sink water into dishwasher.
6. Tin S and sensible are right. The drain hose from the dishwasher needs strapped up as high as possible under the counter top. This prevents the waste water from running back into the dishwasher. It is very important to get that hose higher than the bottom of the sink. It needs to be tucked up by the faucet.