The short answer
A DWS dishwasher that leaves film on glass and grit on the lower rack is usually telling you that flow, not chemistry, has dropped. The generic article opens with detergent dose and water temperature; on this platform the filter stack and the spray-arm feed come first because they are what actually starve the upper rack.
What you observe
- Upper rack noticeably worse than the lower — Classic starved-feed tell: the top arm gets what is left after the bottom one takes its share.
- Detergent left undissolved in the dispenser — Either the dispenser flap is obstructed by tall items or the water is not reaching it.
- A gritty deposit that returns within a day of a clean cycle — Soil being recirculated rather than carried away, which is a filter finding almost every time.
- NEAR MISS - standing water in the tub at the end — That is a drainage fault, not a cleaning one, and it belongs on the drainage page.
Causes, most likely first on DWS
- Blocked or unseated spray arms — Ranked first on the DWS family: the wash pattern is made by a small number of jets, and a single seed or paper label takes a whole sector of the rack out of the wash. These codes share a tub and a wash system, so a finding on one of them is worth assuming on the rest. This moves above loaded or seated-badly filter stack, which leads the brand-generic order, because the family spans several sizes on one platform and it is the shared parts that wear.
- Loaded or seated-badly filter stack — Second: the machine washes with the same water for the whole cycle, so once the fine mesh is loaded that water carries soil back onto the load instead of away from it.
- Wash-pump wear or a worn impeller — Third: a pump that has worn pressurises the arms weakly, which produces a clean-looking machine with nothing blocked and a result that is still poor.
- Throttled fill: inlet screen, valve or a part-closed stop tap — Fourth: the fill is judged by level rather than by clock, so a restricted supply can still satisfy the control and run an entire cycle underfilled.
- Detergent, rinse aid and water temperature — Last: worth confirming, but dose and temperature explain a marginal wash rather than a badly dirty one on a machine with a clear flow path.
Check in this order, and why
- Pull and inspect the filter stack — Two minutes, no tools, and it settles the most likely cause before anything is dismantled.
- Look at the dispenser flap and what is loaded in front of it — A tall item blocking the flap stops the detergent reaching the wash at all.
- Feel the water temperature at the nearest tap first — Cold incoming water lengthens every cycle and softens the result without breaking anything.
- Run a short cycle empty with the door cracked at wash — You are checking that the pattern hits both racks; do this only once the power question is settled.
Before you open anything
Safety
Isolate the machine at the breaker and shut the stop tap before any panel or fitting is disturbed. Broken glass in the sump is the injury that actually happens here, so lift debris with pliers and not with fingers.
When to call a technician
Stop at the point where the wash pump itself is suspect. Filters, arms and the inlet screen are owner work on this family; a pump or a circulation-heater fault means the machine comes out of the cabinet, and on a built-in installation that is a two-person job with the water off.
Other DWS pages
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
