Dishwasher not cleaning properly: what to check

Start with the parts that water needs to pass through.

The answer in 2 lines. Check the filter, spray arms and loading before assuming an internal part has failed. Then check the detergent instructions, salt and rinse-aid indicators. Switch off and isolate the appliance before maintenance, and let it cool. Persistent poor results, leaks, unusual electrical symptoms or recurring errors need professional investigation.

The first checks

Inspect the filter. With the appliance isolated and cool, remove and clean the accessible filter as your manual describes, then secure it correctly.
Check the spray arms. They must not catch on plates, utensils or tall dishes. Clean removable arms only as instructed for your model.
Review the load and settings. Leave room for water to reach dirty surfaces, keep the detergent dispenser clear and select a programme suitable for the load.

Stop: danger

Water near electrics: do not touch a wet plug, socket or switch. Stop using the appliance and arrange safe isolation and assessment.
Scorch marks, crackling, overheating or repeated tripping: stop using it and disconnect only if safe. Do not keep resetting the circuit.
Fire or smoke: get out and call 999. Do not delay your escape to investigate. Follow the official fire escape instructions if you cannot leave safely.

Match the problem to the check

Food particles can indicate a dirty filter or obstructed water circulation. Uneven results between baskets make loading and spray-arm movement worth checking. White marks can have different causes: review the water-softener setting, salt and rinse aid rather than simply adding more detergent.

Use Which?'s dishwasher cleaning guide to identify the maintenance steps. Compare each with your manual before removing a component. Cleaning will not resolve every pump, heating or control fault.

Clean without damaging the machine

Rinse the removable filter and use a soft brush where appropriate. Take care around trapped debris, which may include broken glass. For removable spray arms, rinse away blockages without enlarging the openings, then refit them securely.

Top up salt and rinse aid when required by the appliance instructions. Put each product in its designated reservoir. If your manual specifies a maintenance programme, follow its product and loading instructions. Never assume every dishwasher needs the same treatment.

What not to do

Adding washing-up liquid or cleaning products that are not recommended for the appliance.
Using extra detergent as a substitute for clearing blocked filters or correcting loading.
Removing panels, reaching into pump mechanisms or dismantling an integrated appliance for a routine check.

When to arrange a repair

If results remain poor after appropriate maintenance, record the programme, products used, warning messages and whether the problem affects the whole load. Photographs of the results can help explain an intermittent issue.

Ask a qualified appliance repairer for written charges before booking: diagnosis, labour, parts and any further visit. Describe the symptoms rather than requesting a particular replacement part.

Check the official recall search using the appliance details. Match the model identifiers and follow any applicable notice before further use.

Contact the seller before paying

In England, an appliance bought from a trader must meet the applicable standards for quality, purpose and description. A commercial warranty does not replace your statutory rights, and its expiry does not automatically end them.

A qualifying fault appearing within six months is normally presumed to have existed at delivery unless the seller shows otherwise. Later, evidence may be needed. Misuse, accidents and ordinary wear do not automatically create a right to a free repair.

Use Citizens Advice's faulty-goods guidance to check your position and prepare your request. Choose the relevant country advice if you live in Wales, Scotland or Northern Ireland.

Good to know

Keep the receipt or other proof of purchase, fault photographs and written exchanges with the seller before authorising paid repairs.
Use Electrical Safety First's dishwasher guidance to review installation and warning signs. Avoid extension leads and running the appliance overnight.

Illustrative example: in Birmingham, Daniel finds food on the upper basket's dishes. With the machine isolated and cool, he checks the filter and discovers that a tall utensil obstructs a spray arm. He cleans the accessible parts and rearranges the load. If the next suitable programme still leaves dishes dirty, he will record the results and contact the seller or a repairer.

A made-up story, for illustration.

Bobby

Sources, verification, confidence

Verified on 5 November 2026, for England. Confidence: high for electrical safety and general consumer rights; medium for maintenance and symptom interpretation, which depend on the appliance. No universal cleaning interval, repair tariff or national fault-frequency figure is asserted.