Commercial dishwashers often don't wash dishes - that isn't their purpose. Most often, you need to rinse off any solids and scrub off anything baked on (which happens, especially with buffet-style inserts). After removing obvious dirt, they go into the dishwasher, which realistically is there to sanitize the dishes. If you don't have this, you generally need 3 sinks so you can have a sink full of disinfectant.