Dishwasher Not Cleaning Properly? What to Check First
Why dishes come out dirty or cloudy, and the checks to make on spray arms, filters, loading, detergent and water supply before calling an engineer.
When dishes come out gritty, greasy or cloudy, most people assume the dishwasher is failing. In reality, the cause is more often loading, detergent or a blocked filter. A methodical check usually finds the problem in minutes and costs nothing.
Start with loading
How you load makes a big difference.
- Do not block the spray arms with tall items.
- Face dirty surfaces toward the centre and the spray.
- Avoid nesting bowls and spoons, which hide soiled areas.
- Do not overload the racks, because water cannot reach every item.
- Scrape off large food scraps, but there is no need to pre-rinse fully.
Check the filter
The filter sits in the bottom of the tub and catches food particles. If it clogs, water flows poorly and debris is redeposited on dishes.
- Remove the lower rack.
- Twist and lift out the filter assembly, following the manual.
- Rinse it under warm water, scrubbing gently with a soft brush.
- Check the sump beneath for objects such as labels, bones or fragments of glass.
- Refit it securely.
Cleaning the filter monthly is a helpful habit.
Spray arms
Spray arms have small holes that can clog with scale or food.
- Remove the arms if they unclip and check that they spin freely.
- Clear the holes with a toothpick or a similar tool.
- Rinse them and refit, making sure they are seated.
Detergent, rinse aid and salt
Detergent
Use the correct amount and type. Too little leaves residue, and too much can cause cloudy glass. Tablets may not dissolve fully on short, cold programmes, so use a longer cycle if you see undissolved tablet remains.
Rinse aid and salt
Rinse aid helps water run off glass and reduces spots. If the rinse aid compartment is empty, glasses may be spotty. In hard water areas, a dishwasher with a water softener needs salt, and when it runs out, limescale builds up, leaving a white film. Check both reservoirs and top up as needed.
Water and temperature
| Problem | Likely cause |
|---|---|
| Dishes cold, greasy | Heater or thermostat fault, or low temperature programme |
| White film or cloudy glass | Hard water, empty salt or rinse aid |
| Food residue | Blocked filter or spray arms |
| Detergent left in dispenser | Door catch fault or blocked spray arm |
| Low water level | Inlet valve problem or closed tap |
Check that the tap behind the machine is fully open and the inlet hose is not kinked. If the water supply has recently been off, or pressure is low, the machine may not fill correctly.
Clean the machine itself
Run an empty hot cycle with a dishwasher cleaner or the amount of descaler recommended in the manual. Wipe the door seal and edges, where grease collects. Our guide to washing machine smells uses a similar approach for another appliance.
When it needs an engineer
Call for help if the machine does not heat, does not drain, has a failed pump or shows persistent error codes. Intermittent faults and heating issues usually need testing. Describe the symptoms using our fault description guide.
If the machine is more than about ten years old and the repair is expensive, weigh up the cost using the repair or replace rule of thumb. You can also request offers on Compito to compare local providers.
A quick step-by-step routine
Switch off at the socket before you reach into the machine, and let the interior cool if a cycle has just finished.
- Remove everything and look for anything blocking the spray arms.
- Take out and rinse the filter and check the sump for debris.
- Check the spray arm holes and the detergent door.
- Run a hot, empty cycle with a machine cleaner.
- Re-test with a normal load and a fresh tablet or powder.
If dishes are still dirty, change one variable at a time. Switching detergent, salt level and programme all at once makes it impossible to tell which helped.
Common mistakes
- Using a short eco programme every day for greasy pans, which may not give detergent time to work.
- Putting wrapped or gel-coated tablets in the cutlery basket where they do not dissolve.
- Loading plates facing away from the spray arm.
- Ignoring a smell, which often means a dirty filter or sump.
- Running the tap hot before starting to compensate for a heater fault.
Hard water, soft water and the salt setting
If you are in a hard water area, the salt setting should typically be adjusted to match. A water supplier's local hardness information, or a simple test strip, can tell you what to set. Too low a setting leaves a white film, whereas in a very soft water area you may need much less detergent than the pack suggests.
Rentals and older machines
In a rented home, tell the landlord if the machine will not heat or drain, since supplied appliances are usually their responsibility. On machines over about ten years old, a worn pump or heating element is a common reason for poor results.
Frequently asked questions
Why are my glasses cloudy?
Often hard water, too much detergent or a lack of rinse aid. Some cloudiness is etching, which is permanent damage to the glass, and cannot be cleaned off.
Should I rinse dishes before loading?
Scraping is enough for most machines. Heavy pre-rinsing wastes water and can make detergent less effective.
How often should I clean the filter?
A monthly check is a good habit, more often if you cook heavily or do not scrape plates.
Can I use washing-up liquid in a dishwasher?
No. It creates excessive foam and may flood the machine.
Why does my dishwasher leave a gritty feel on dishes?
Grit usually comes from a clogged filter redepositing food debris, or from undissolved detergent. Clean the filter and spray arms, then try a longer programme.