That strange round silver R2-D2-looking thing, to the side of the kitchen faucet, is the dishwasher’s air gap. When it gets full of gunk from debris left on dishes, the dishwasher can’t drain.

A small cylinder piece next to your sink could be the reason for the backup as well. This piece, known as an air gap, helps create space between the clean, running water and the dirty water from the ...