How does a dishwasher actually clean without scrubbing?

Through a combination of high-pressure water, heat, and chemistry that is considerably more aggressive than washing-up liquid — and the chemistry does most of the work people attribute to scrubbing.

The mechanical part. Water is pumped at pressure through spray arms that rotate by reaction force, directing jets across the load from below, between and often above. This provides mechanical energy, but it is nothing like scrubbing — it is force applied briefly and indirectly, which is why loading matters so much. Anything blocking a spray arm or shadowing another item will not be cleaned.

The chemical part, which is the crucial difference. Dishwasher detergent is strongly alkaline — far more so than hand washing-up liquid, and not safe for skin contact. Alkalinity saponifies fats, converting grease into soap-like compounds that rinse away, and it breaks down protein soils.

Detergent also contains enzymes — proteases for protein, amylases for starch — which digest food residues, plus bleaching agents for tea and coffee stains and anti-redeposition agents stopping loosened soil settling elsewhere.

Heat accelerates all of this and helps dissolve fats.

Why you should not pre-rinse. This surprises people. Modern machines use turbidity sensors measuring how dirty the water is to decide cycle intensity. A pre-rinsed load reads as clean and gets a gentler cycle. Enzymes also need something to act on. Scrape solids off; do not rinse.

Salt and rinse aid are doing distinct jobs:

Salt regenerates the machine's built-in water softener, removing calcium so limescale does not build up and detergent works properly. Needed in hard water areas regardless of all-in-one tablets.

Rinse aid reduces water surface tension so it sheets off rather than beading, preventing spots and improving drying — which matters because most machines now rely on condensation drying with no heating element.