The short answer
On the Black Decker WQP dishwasher a load that comes out dirty is usually water not reaching the dishes rather than water that cannot clean them. The WQP stems step through sizes on a common mechanism, so the sequence below applies across the model list in the table.
What you observe
- A gritty film on everything, top rack and bottom alike — Uniform across the load.
- Clean at the front, dirty at the back — or the reverse — A pattern is the most useful thing a bad wash can give you: it maps directly onto where the spray is not reaching.
- Food debris redeposited on the upturned faces of bowls — The filter is passing what it caught back into the wash, which is a filter and sump problem before it is anything else.
- NEAR MISS — dishes are wet as well as dirty — A load that does not dry either points at the heat and the cycle itself, and the heating page will take you further than this one.
Causes, most likely first on the WQP family
- Spray arm holes and free rotation — First on this family — the WQP stems step through sizes on a common mechanism — and a compact wash chamber gives the arm very little clearance: one tall item catching a blade stops the sweep, and a handful of blocked holes collapses the pressure across the rest. It leaves a pattern, and the pattern names the arm.
- Filter and sump loaded with debris — Second. Once the filter is full the pump recirculates what it has already collected, so every load finishes dirtier than it started. On this class it is the single most neglected maintenance item.
- Loading: overlap, shadowing and oversized items — Third, and no part will fix it. A tray packed to the edges blocks the spray from everything behind it, and a baking sheet across the lower rack shields the entire back of the chamber.
- Water temperature, detergent and hardness — Last on this ranking because it produces an even film rather than a pattern — but it is the answer whenever the whole load is uniformly poor rather than patchy.
Check in this order, and why
- Spin both spray arms by hand and look through the holes — First because it is instant and because a stopped or blocked arm explains any pattern in the load before anything is dismantled.
- Pull the filter and clean the sump — Second: it is the top maintenance cause, and a filter full of debris makes every later test meaningless.
- Run a short cycle empty and open the door mid-wash — Third — a face full of hot spray says the machine is delivering, which moves the investigation to loading and chemistry.
- Check how hot the water arriving is — Last of the free checks: run the sink tap hot before starting, and see whether the same load improves.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel — a capacitor can hold a charge after the power is off. Shut the water supply before disturbing a hose or a coupler. Wash water is hot enough to scald, so let a cycle finish before opening a door fully, and never reach into a sump without power off: broken glass is the usual find there.
Models in the WQP family
Reference| Model number | Family key |
|---|---|
| WQP12-5901K-US | black-decker:dishwasher:wqp |
| WQP12-6502A | black-decker:dishwasher:wqp |
| WQP12-6503 | black-decker:dishwasher:wqp |
| WQP6-3603-US | black-decker:dishwasher:wqp |
| WQP8-P7606F-US | black-decker:dishwasher:wqp |
When to call a technician
Call when the arms spin freely, the filter is clean, the supply is hot and the load still comes out under-washed — at that point the wash pump or its seal is the remaining suspect and it needs the machine out and on its back. Call sooner if you find water under the unit while investigating, or if the sump is full of broken glass.
Other faults covered for the WQP family
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
