A dishwasher rarely dies all at once. Its cleaning power fades a little at a time — a film on the glasses here, a bit of grit on a plate there — until one morning you unload a full rack that looks like it only got rinsed. The system itself is simple: water gets pumped out through spinning arms, and if the water is hot, the filter is clear, and the arms can actually spin, dishes come out clean. When they don't, something in that short chain is off. Work through these checks in order; they're sorted so the free, five-minute fixes come first.
Clean the filter. This is the number one cause, and most owners don't know the filter exists. At the bottom of the tub, under the lower spray arm, there's a cylindrical filter that twists out — usually a quarter turn counterclockwise. Rinse it under the tap and scrub off the gray film with a brush. That film is trapped food grease, and once it coats the mesh, dirty water recirculates over your "clean" dishes all cycle long. Put a reminder on it: monthly is about right for most households.
Check the spray arms. Flick each arm with a finger — it should spin freely and keep going. Then look along the arms for holes plugged with seeds, bits of label, or white mineral crust. Poke each hole clear with a toothpick. Many arms lift off or unscrew so you can rinse them out from inside. Pay attention to the top arm especially: if the bottom rack comes out fine but the top rack stays dirty, the upper arm is the first suspect.
Give it hot water from the start. Most dishwashers fill with whatever is in the hot water line — and if nobody has run the kitchen tap in hours, the first fill or two is cold. Detergent barely works in cold water. Run the sink tap until it steams before you start the machine. While you're at it, check your water heater setting: around 120°F is the usual target. Well below that, grease just doesn't let go.
Load it so the water can reach. Face the dirty surfaces toward the center and angle them down at the spray. Don't nest bowls or stack spoons together — nested items come out exactly as dirty as they went in. Slide the upper arm after loading and spin it by hand to be sure a tall pan or cutting board isn't blocking it. And check that nothing tall on the bottom rack is stopping the detergent cup door from flipping open; a door that never opened means the whole cycle ran on plain water.
Look at the detergent itself. Powder that has sat open in a damp cabinet for a year clumps and loses strength. Pods tossed in the bottom of the tub dissolve too early; they belong in the dispenser. If your water is soft, a full dose is often too much — excess detergent redeposits as film. Cloudy glasses call for rinse aid, which helps water sheet off instead of beading up and drying into spots.
Run an empty cleaning cycle. Months of grease and mineral scale line the tub, the arms, and the sump, and they dull performance even when every part works. Set a cup of white vinegar upright on the top rack and run the hottest cycle empty, or use a purpose-made dishwasher cleaner. You'll smell the difference, and the spray arms usually pick up speed.
| What you see | Likely cause |
|---|---|
| Grit and sand on dishes after the cycle | Clogged filter recirculating dirty water |
| Bottom rack clean, top rack still dirty | Upper spray arm blocked or not spinning |
| White film that wipes or vinegar-soaks off | Hard water deposits — add rinse aid |
| Cloudiness that won't come off at all | Etched glass (see the note below) |
| Detergent still in the cup afterward | Dispenser door blocked or failed to open |
| Everything a little dirty, nothing terrible | Cold fill water or worn-out detergent |
Pre-rinsing everything. Scrape plates, sure, but don't wash them before they go in. Modern detergents are enzymes that need food soil to work on, and a load of already-clean dishes can leave detergent with nothing to do except cloud your glassware. Chronically dirty results also hide longer on pre-rinsed loads, because the machine never gets a real test.
More detergent as the answer. When dishes come out dirty, pouring in extra detergent feels logical and usually backfires, especially in soft water — the surplus ends up as white residue. Fix the water flow first; dose second.
Ignoring a torn filter. If the filter mesh is ripped or the housing is cracked, grit flows straight back onto the dishes and can wear on the pump. A replacement filter is a cheap part; a pump is not.
If you've done all six steps and loads still come out dirty, listen to a cycle. You should hear the tub fill, then a strong, steady spray. Weak, sputtering spray with a clean filter points to a tired circulation pump. Almost no water in the tub points to the inlet valve or its mesh screen. Dishes that come out cold, with no puff of steam when you open the door, point to a failed heater. Those are repair-tech jobs — and before you book one, it's worth a quick look at how long home appliances last, so you can judge whether a repair bill makes sense for a machine of its age. A different symptom entirely — a tub that won't empty — is covered in our guide to a dishwasher that won't drain. And water appearing on the floor rather than in the tub points to a leak instead — our guide to a dishwasher leaking water on floor sorts those by source.
Bottom line: A dishwasher that's stopped cleaning is almost always a maintenance problem wearing a breakdown costume. Filter, spray arms, hot water, sane loading — an hour of free work restores most machines. Only start pricing repairs when the spray itself sounds weak.
Usually the filter. Once it's coated in grease, the machine washes your dishes in recycled dirty water for the entire cycle. After that, check the spray arm holes for clogs and run the kitchen tap hot before starting, so the first fill isn't cold.
About once a month for most households. If you load heavily soiled dishes daily, or you start seeing grit on glasses, do it sooner. It takes two minutes: twist, rinse, scrub, twist back in.
Two possibilities. A white film that wipes off or dissolves with vinegar is hard-water mineral deposit — rinse aid and a cleaning cycle handle it. Cloudiness that never comes off is etching, permanent surface damage common with soft water and too much detergent; lowering the dose prevents it on the rest of your glassware.
Scrape off chunks, but skip the rinse. Today's enzyme detergents are built to attack food soil, and a nearly clean load can actually come out worse, with clouded glassware. Let the machine do the job you bought it for.
Yes, for routine freshening: a cup of white vinegar on the top rack, hottest cycle, empty tub. Commercial cleaners are stronger on heavy mineral scale. Either way, the cleaning cycle only pays off if the filter and spray arms are clear first.