Dishwasher Not Cleaning Dishes? 7 Common Causes

When a dishwasher is not cleaning, leaving food stuck to plates, grit in the glasses or a cloudy film, the machine usually is not broken. Common causes are a dirty filter, blocked spray arms, water that is not hot enough and detergent problems, and you can fix all of them yourself. If the dishes are still dirty after the checks below, a pump or heater has probably failed, and that is a repair.

If there is also standing water in the bottom of the tub, start with our dishwasher not draining checklist instead. If the dishwasher will not run at all, see dishwasher won't start.

Checks you can do yourself

These seven checks match the seven common causes, in the order to try them. Switch the dishwasher off at the breaker, or unplug it, before you reach into the tub, and give the heating element in the floor time to cool.

1. Clean the filter. Many modern dishwashers have a filter in the floor of the tub that you clean by hand, and when it clogs, water flow drops and food ends up back on the dishes. On many Whirlpool models you turn the upper filter assembly a quarter turn counterclockwise and lift it out. On Bosch and GE models the filter also sits at the bottom of the tub; your manual shows how it comes out. Rinse it under running water, and use mild soap and a soft brush on stubborn bits, as Bosch recommends. Lock it back in place, and never run the dishwasher without it.
2. Clear the spray arms. Spin each arm by hand; it should turn freely. Then remove the arms (your manual shows how), run them under water to see if any holes are blocked, and loosen any debris in the holes with a toothpick, as Bosch recommends. A paper clip or tweezers also works, as long as you take care not to damage the arm.
3. Load so the arms can spin. A tall pan, a cutting board or a utensil hanging through the rack can stop an arm cold. GE says all items should face down toward the spray arm and nothing should block the wash system, and it suggests spinning the spray arm before every load. Leave space between items and do not overload the racks.
4. Run the hot water at the sink first. Water should be about 120°F or hotter as it enters the dishwasher. Run the kitchen tap for 30 to 60 seconds before you start the cycle; to check, fill a cup and use a thermometer, as Whirlpool suggests. If the tap never gets that warm, the water heater should be set to deliver at least 120°F, and it helps not to run the dishwasher right after showers or baths.
5. Use fresh detergent, rinse aid and the right cycle. GE says to discard detergent that is old or lumpy, because it may not dissolve and can leave a gritty residue, and to store it sealed. Use high-quality pre-measured tablets or packs, and keep the rinse aid dispenser filled, because rinse aid helps both washing and drying. For baked-on food, use a heavier cycle or a high-temperature option, and remember that a Top Rack Only cycle does not run the lower spray arms on Whirlpool models.
6. Deal with hard-water film. A chalky white film on glasses and inside the tub is usually mineral buildup, and it clogs spray-arm holes too. Whirlpool suggests a dishwasher cleaner or white vinegar to remove mineral deposits, and a water softener for very hard water. A dishwasher descaler used a few times a year also helps. Hardness depends on where your water comes from: your water utility can tell you how hard its water is, and a water test will tell you if you are on a private well.
7. Listen to the wash. With the filter, arms, water and detergent sorted, run an empty cycle and listen. A steady swish of water means the pump is spraying. A hum with little or no splashing points to the circulation pump. Dishes that come out cool, wet and greasy after a normal cycle suggest the water is not being heated.

Dishwasher not spraying water or wash arm not spinning

If the dishwasher runs but the dishes come out barely wet, or one rack is always dirtier than the other, water is not reaching the spray arms with enough force. Work from simple to serious:

• Something is blocking the arm. Whirlpool says to spin the middle spray arm by hand before a cycle to make sure nothing stops it. Rearrange the load if it catches.
• The holes are clogged. Clean them as described above; Whirlpool notes that hard-water mineral deposits build up on spray arms too.
• The arm is cracked or loose. A cracked arm leaks pressure, and a loose or missing mounting nut lets it wobble instead of spin. Replacement arms are inexpensive.
• Too little water. Whirlpool says the water supply valve must be completely open, and household water pressure should be between 20 and 120 psi. A failing inlet valve can also let in too little water.
• A weak circulation pump. If the filter and arms are clean and you hear a hum with little spraying, the pump that drives the spray arms may be failing.

Whirlpool dishwasher not cleaning

If you own a Whirlpool, the company's own guidance lines up with the checks above, with a few specifics worth knowing:

• Clean the filter about every 30 days.
• Incoming water should be about 120°F.
• The water supply valve must be completely open, with pressure between 20 and 120 psi.
• Pre-measured tablets or packs are recommended over powder, liquid or gel, and rinse aid matters for spotting and drying.
• Water with 15 grains of hardness per gallon or more can damage the dishwasher and make good results difficult to achieve; Whirlpool recommends a water softener.
• Never use dish soap in the dispenser. Whirlpool warns that it makes excess suds that keep the dishwasher from washing properly.

If you have done all of that and the dishes are still dirty, the problem is mechanical.

GE installation checks

GE's own wash-performance checklist adds three installation points worth ruling out, especially in a newer kitchen:

• The dishwasher should be connected to the hot water line, not the cold.
• It should be level side to side and front to back.
• GE says a drain hose installed more than 72 inches high will not drain well, and that hurts wash performance too.

What usually fails

When the filter, arms, water temperature and detergent all check out, one of these parts is usually to blame:

• Circulation pump (wash motor). It drives water through the spray arms. A weak pump leaves both racks dirty, and you may hear a hum with little spraying.
• Heating element or thermostat. If the water never gets hot, the detergent cannot do its job. Signs include greasy dishes, dishes that stay wet and cycles that run far longer than normal; Whirlpool notes that a dishwasher fed cold water spends extra time trying to reach its programmed temperatures. On some models the heater is built into the pump assembly.
• Water inlet valve. Too little water means too little spray.
• Detergent dispenser. If the detergent is still sitting in the cup after a cycle, the dispenser door is not opening.
• Spray arm. Cracked, warped or missing its mounting nut.

A pump, heater or valve fault takes testing to pin down, and that is where circulation pump and heater repair comes in: the technician tests first and quotes the repair in writing before any work starts.

What it costs in Atlanta

The diagnostic is $80 and is waived when you approve the repair. Dishwasher repairs start at $180 plus parts, quoted in writing as a flat rate before any work begins. On standard brands, typical dishwasher repairs run about $250 to $430 all in; spray arms, dispensers and inlet valves are at the lower end, and circulation pumps and heaters cost more. See typical total costs. The repair is done on the first visit when the part is in stock, and every repair carries our 60-day parts-and-labor warranty.

Repair or replace?

As a rough estimate, InterNACHI's life-expectancy chart puts a dishwasher at about 9 years, so a pump or heater repair on a younger machine is usually worth pricing out. A cracked tub is the exception. Our repair-or-replace guide has the details.

Keep it cleaning

• Scrape plates instead of pre-rinsing them, and clean the filter monthly.
• Keep rinse aid topped up and detergent sealed and dry.
• Run the kitchen tap hot before each cycle.
• Clear the spray-arm holes every few months, as Bosch suggests.

Schedule a visit or read about our dishwasher repair service. Prefer to talk? Call (470) 778-4087.