My dishwasher does not completely drain itself – why?

Dishwashers are supposed to leave some water in the unit at the end of each cycle. This is to keep the element type heater, used for drying the dishes, from burning up. It’s a lot like a water heater element. If a lot of water stays in the sump – the drain could be clogged. A partially clogged air gap will do the same thing. The air gap is that little chrome dome on the kitchen counter.