Water Backing Up Into Dishwasher


Our dishwasher is located to the left of the double sink and the garbage disposal is on the left side too but the main drain is located under the right side. So water from the dishwasher and garbage disposal is piped over to the right and then down. Water frequently backs up into the dishwasher, sometimes pouring onto the floor, while I am cleaning up unless I am very careful to keep the flow of water very low. The main drain is on the back right wall so the dishwasher and left side water must be piped over to it. Could this be rearranged so that the water would stop flowing into the dishwasher?


There are two ways to address this problem. In some areas, code requires the dishwasher drain line to be plumbed up into an “air gap” that is positioned at the sink. The air gap prevents siphoning of water back into the dishwasher. However, it can be hard to retrofit an air gap in cases where the counter or sink does not have a hole designed for it.

The other option is to make sure the dishwasher drain hose has a “bump” in it, so that it rises higher than the sink bottom before descending to connect to the garbage disposal.  Any siphoning of water will then rise up out of the sink before finding its way to your dishwasher, and onto your floor.  This is very important and you can find a number of pictures of how this would appear underneath your sink.  I once had a customer who had a similar problem except that drain was plugged up and required some work to get to.  There seemed to be countless number of mouse traps that were set off in the process of performing the work.  Once I got back in there I was surprised to see that the hoses all tangled up without the proper configuration that I described.

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