Houzz Logo Print

Dishwasher discharge with no p-trap

16 years ago

The dishwasher discharge line is required to go up as high as possible under the countertop then drop down below the disposal before attaching to the disposal inlet. The high loop creates a natural trap to prevent the backflow your desribing.

I noticed the above quote from another thread regarding dishwasher backfilling.

It got me wondering about my dishwasher. My discharge line goes from where ever it is connected to the dishwasher and comes in under the kitchen sink just below the counter top. But then it goes to it's own waste water stub. I'm guessing because the two stubs (one for dishwasher, one for sink) on connected together behind the wall, my dishwasher discharge line still goes up high just to insure that it's impossible for waste from the sink to get into the dishwasher.

But I also noticed that the discharge line does not go through a p-trap before getting connected to the stub. Does that mean that the dishwasher itself has a built in p-trap to prevent sewer gases from backing into the dishwasher... or was the connection done in error?

Comment (1)