Plumbing Question

Hi, Ever heard of check vaqlve? If you don't use dish washer once in a while at least, the seals can dry out and it'll become useless causing water leaks.

Be sure the drain hose is looped up high from the DW to the disposal. You can also use an air gap to prevent backflow.

Yes, those are the two methods. Some places, code requires an air gap. I've always used the high loop method and had no problems. The hose should come up to the underside of the counter top.

The BEST way , ( i can't imagine where you'd put an air gap that was effective) is to tee the dishwasher line into the sink drain line away from the disposer. I suspect your disposer is acting somewhat like a pump when you dump big loads of water and whatever with it on and is forcing the water back down that little line. If it is a double sink, just tee the dishwasher line into the other sink line.