Kitchen sink fills with water when the dishwasher drains.

Any clog or blockage within that main drainage line can cause water to backup and overflow into your kitchen sink. These clogs typically occur in four places: the dishwasher, the garbage disposal, the sink, and the air gap. I'd suggest starting by checking these spots for clogs.

All the above, but it also depends on how old is your house. We had a 1940's house and my washing machine always filled my laundry sink and drained slow. We made sure that there were no cloggs, then call a plumber friend and found out that the old pipes leading to sewer, were small and the machine was pumping the water out faster than the pipes could flow. Not cheap to change.

Had the same problem. Plumber said the dishwasher had not been plumbed correctly. Instead of separate drain it had been plumbed to go through the disposal.

Dishwashers are supposed to drain through the disposal, so any food remains end up there. I have never seen one with a separate drain! I would suggest you have a partial blockage in the drain pipe leading from the disposal to your main drain line. It's not too hard to check. Most times, you can remove the drain line be loosening the pipe connections by hand, or with a large pliers.

I would be getting a bottle of Roebic Drain Cleaner and a bottle of their Root Killer. Mix the right amount of the Drain Cleaner in warm water and put down the sink before bed, its not caustic... its enzymes that eat the crud, and then run Hot water in the morning. I would also do the same with the dishwasher and run it in the morning. Then see if it drains better.

I run the Root Killer every fall before the rains to make sure I'm getting the

best sewer action when the rains come.

Agree to all the previous advice! But a simple add'l thing to check- before you run dishwasher, be sure to run disposal first to make sure no clog there.

Yes, great idea.