Why is there water standing in the bottom of the dishwasher tub?

A small amount of water around the outlet on the tub bottom at the back is normal — it is clean water that keeps the water seal lubricated. However, if the entire bottom of the tub has water, you may have a drain problem and should check and clean the air gap if you have one. You should also check whether your kitchen sink is draining properly, and if the dishwasher drains into a disposer, run the disposer to clear any clogs. (Page 13)