Rinse aid lowers water surface tension during the final rinse so water sheets off more easily. That can reduce droplets, mineral spotting, and wet dishes, especially with hard water or energy-efficient drying. It is not detergent and goes in a separate dispenser when the dishwasher supports it.
It helps water sheet off surfaces
With fewer large droplets left behind, there is less water to evaporate and fewer spots where minerals concentrate as they dry. The effect is often most noticeable on glass, steel, and hard-to-dry plastics.
It does not replace detergent
Detergent removes grease and soil during washing; rinse aid acts mainly during rinsing and drying. Do not pour rinse aid into the detergent cup or detergent into the rinse-aid reservoir.
Adjust the setting if spotting or residue remains
Many dishwashers let you change how much rinse aid is dispensed. If droplets persist, increase gradually; if bluish film or unusual foaming appears, reduce the setting and confirm the correct product is being used.
Hard water may need more than rinse aid
Rinse aid can reduce spotting but does not remove all minerals from the water. With severe hardness, also check dishwasher salt where applicable, hardness settings, and manufacturer-recommended descaling.