Grades 3–5 · Machines
How does a dishwasher wash dishes without filling to the top?
A dishwasher is not a bathtub full of dishes. A shallow pool at the bottom supplies water to a circulation pump. The pump raises the water's pressure and sends it through spray arms, where small openings direct jets toward plates, cups and other surfaces.
In the diagramA shallow pool makes a repeated wash loopWash water returns to the bottom; draining uses an exitPumpFiltered returnSpray armJets hit dishes; water falls back to the sump for another pass.
The arms can rotate, sweeping their jets across different parts of the cabinet. A dish does not need to remain underwater for moving water to reach it. Heat, detergent and the force of the water help loosen food, and the flowing water carries loosened material away from the surface.
Water falls back into the bottom pool and goes around the wash loop again. A filter catches food particles, helping protect the pump and reducing the amount of debris sent back through the jets. Filtering keeps particles out of the circulating route; it does not turn the used wash water into fresh water.
Later, a separate drain pump sends the dirty water out. Fresh water enters for rinsing, circulates over the dishes and drains away too. Drying follows, with methods that vary between machines. Reusing water during a stage and replacing it between stages are different jobs, and their timing explains how a shallow pool can wash a whole cabinet.
About this explanation
Starting knowledge: Understand a pump moving water and distinguish returning water from drained water.
Sources
- Whirlpool — How Does a Dishwasher Work on the Inside?
- Whirlpool — Parts of a Dishwasher: A Quick Reference Guide