Dishwasher - Wash Zones
Introduced in the year 2012, this dishwasher feature allows you to choose to wash only the Upper rack or only the Lower rack. The benefit of this feature is that you do not need to wait to get a full dishwasher load to run a cycle. The Upper or Lower Rack wash can be used in combination with most wash cycles and options. You just choose the cycle you want along with any options, then choose your wash zone: Upper or Lower.
Upper Wash Zone:
The spray arm or hub on the tub ceiling and the middle spray arm are used.
Lower Wash Zone:
The middle spray arm and lower spray arm are used.
If your dishwasher has this feature, you may want to take a look at the Owner's Manual for the dishwasher model to see how the Wash Zones feature is used.