Dishwasher wont drain?

The most obvious cause is that the homeowner neglected to run the garbage disposer before starting the dishwasher. In this region, most dishwasher drain hoses attach to a drain opening in the side of the disposer. If the disposer is full of food waste, or not operating, (i.e., stopped up ,or broken) there is no way that the dishwasher can drain. Before you push the panic button, run the disposer, then try to drain the dishwasher.  Many dishwashers have a cancel/drain feature which will accomplish this.