A dishwasher cleans with four things: hot water, enough of it, spray pressure, and detergent that gets released at the right moment. When dishes come out gritty, one of those four is missing, and the job is to work out which. Be precise about the symptom first, because it points at different faults — food particles left stuck on is a spray or filter problem, a chalky white haze is a water hardness and rinse aid problem, and food redeposited as a fine grey film across everything is a filter or drain problem. This guide covers the first of those.
Read this first
- Switch the dishwasher off at the breaker before reaching under the machine or removing the toe kick to inspect the inlet valve.
- The sump area under the filter often contains glass shards and staple-sized metal fragments. Sweep it with a paper towel rather than bare fingers.
- Never mix bleach with any dishwasher cleaner containing acid, and never put bleach in a stainless steel tub.
Step by step
Pull and clean the filter, then look under it
Almost every dishwasher built in the last fifteen years has a manual filter in the floor of the tub, and a great many owners have never taken it out. Twist the cylindrical centre section anticlockwise, lift it, and remove the flat mesh plate underneath. Rinse both under hot running water with a soft brush until light passes through the mesh everywhere. Then shine a torch into the sump beneath: broken glass, fruit stickers, olive pits and a sludge of grease collect there and get pumped straight back over the dishes. A filter that is even partly blinded starves the wash pump and drops spray pressure across the whole machine. Clean it monthly.
Check that both spray arms turn freely and clear every hole
Take the lower arm off — most lift or unscrew by hand — and the upper arm too, then hold each up to the light and look through the jets. Clear any blocked ones with a toothpick or a short length of wire, working from the outside in, and flush the arm through under the tap. Look for cracks along the seam and for a jet that has been enlarged or split, because a leaking arm loses the pressure the rest of the jets need. Refit them and spin each by hand: it should rotate with a light push and no scraping. Finally, load the racks as you normally would, then spin the arms again to see what fouls them — a baking tray or a long knife handle stopping the arm dead is one of the most common causes of dirty dishes.
Measure the water temperature at the tap
Detergent enzymes and grease-cutting both depend on heat, and a fill of lukewarm water will not clean regardless of what else is right. Run the kitchen tap hot, hold a cooking thermometer under it, and read the steady temperature — you want to see at least 120°F. If it is lower, the water heater setting is the problem, not the dishwasher. Then deal with the pipe run: the first fill draws whatever is sitting in the line, so run the tap hot immediately before starting the machine. Many dishwashers do have an internal heater that will raise the fill, but it does so by extending the cycle, and some eco cycles do not use it at all.
Confirm it is filling with enough water
Under-filling is common and almost invisible from the outside. Start a cycle, let it fill, then open the door mid-wash and look at the water level in the sump — it should be up to roughly the base of the heating element or the bottom of the sump housing, not a shallow puddle. Too little water and the wash pump draws air, which you can hear as an uneven surging rather than a steady spray. If the fill is short, check that the supply stop under the sink is fully open, and check the inlet valve screen where the water line meets the valve, which silts up with sediment. A valve that hums but passes little water is usually blocked rather than dead.
Look at the detergent, not just the amount of it
Dishwasher detergent degrades with age and humidity: a box or a bag of pods that has been open under the sink for a year cleans noticeably worse than a fresh one, and this is worth ruling out before buying parts. Check that the dispenser flap actually opened during the cycle rather than being blocked by a tall item on the lower rack, an inverted bowl, or a pot handle. If the pod is still sitting whole in the door or half-dissolved on the floor of the tub, the water is too cool or the flap is opening into something. Fill the rinse aid reservoir too, since it affects the final rinse and the drying, and never use hand dishwashing liquid, which will fill the room with foam.
Rethink the loading pattern
Dishwashers clean by line of sight — water has to physically reach a surface. Face soiled sides inward and downward toward the arms, and avoid nesting bowls and spoons inside each other, since two spoons stacked together shield each other completely. Keep large flat items like trays and cutting boards to the outer edges of the lower rack rather than lying across the middle where they form a roof over the lower arm. Leave gaps between items instead of packing to capacity. And stop pre-rinsing: most modern detergents need some soil to work against, and a machine with a soil sensor will select a shorter, weaker cycle if it sees clean water going in.
Check whether the cycle you use is doing enough work
One-hour, express and eco cycles genuinely wash less. They use less water, hold lower temperatures and skip wash phases, and that is the deliberate trade-off for speed and energy. If the machine cleans acceptably on a heavy or pots-and-pans cycle but not on the one-hour setting, nothing is broken. Try a normal or heavy cycle with the sensor wash option enabled and compare the same load. Also check for a rinse-only or a delay option left selected. This step costs nothing and it resolves a lot of complaints on machines that were only ever asked to run their fastest programme.
Inspect the chopper and listen to the wash pump
If the filter fills with a paste of large food fragments after every cycle, the soft food chopper or grinder may be dull or jammed — depending on the design this is a small blade or a screen at the base of the sump. With the power off at the breaker, remove the filter and inspect it for a bone shard or a fruit pit wedged into the assembly. Then listen to a running cycle: a healthy wash pump makes a steady rushing sound, while a grinding, rattling or notably weak note means the impeller is damaged or the motor bearings are worn. Weak spray with a clean filter and clear arms points at the pump rather than at anything you can clean.
What this repair costs
Doing it yourself
$0–$70
Hiring a technician
$120–$400
Prices are general estimates for typical US jobs, not quotes. What you actually pay depends on your appliance's brand and age, the part required, your region, and each shop's labour rate. The DIY figure assumes you supply the labour and buy the part yourself.
Parts you may end up buying
| Part | Install | Typical price | Typical lifespan |
|---|---|---|---|
| Spray Arm | easy | $15–$40 | 5–8 years |
| Inlet Valve | moderate | $15–$40 | 8–12 years |
| Drain Pump | moderate | $35–$120 | 8–12 years |
| Door Latch and Switch Assembly | easy | $20–$80 | 6–12 years |
| Heating Element | moderate | $25–$85 | 8–14 years |
| Float Switch | easy | $10–$35 | 10+ years |
| Door Gasket | easy | $20–$75 | 6–12 years |
| Rack Roller and Adjuster Kit | easy | $12–$50 | 5–10 years |
| Detergent Dispenser | moderate | $30–$100 | 8–12 years |
| Circulation Pump and Motor | advanced | $90–$330 | 8–14 years |
Still not fixed
When to call a pro
If the filter, arms and inlet are all clear, the fill level and water temperature are correct, and the machine still leaves food on the dishes, the wash pump or its diverter valve is the likely fault — and on machines that route water between the upper and lower arms with a motorised diverter, a failed diverter starves one rack while the other cleans normally. Diagnosing that properly means running the service test cycle, which is worth paying for rather than replacing pumps on a guess. Grinding from the pump, or a burnt smell during the wash phase, means stop using the machine and get it looked at.
More dishwasher guides
- Dishwasher Not Draining — Clear the Standing Water20–60 minutes
- Dishwasher Leaking — Find the Source Before It Damages the Floor30–90 minutes
- Dishwasher Not Drying Dishes — Why, and What Actually Helps15–45 minutes
- Dishwasher Soap Dispenser Not Opening — Why the Pod Is Still There20–60 minutes
- Dishwasher Spray Arm Not Spinning — Restore the Wash Action20–45 minutes
- Dishwasher Door Won't Latch or Stay Closed30–90 minutes
- Dishwasher Won't Start — Work Through the Lockouts First30–75 minutes
- Dishwasher Not Filling With Water — Trace the Supply45–90 minutes
- Dishwasher Smells Bad — Clear the Sources in Order45–90 minutes plus a cleaning cycle
- White Film on Dishes — Hard Water Scale or Permanent Etching?30 minutes plus a test cycle
- Dishwasher Making Noise — Match the Sound to the Part30–75 minutes