Why isn't my dishwasher cleaning well?
Updated August 2026
Dishes that come out with grit, film, or dried-on food are almost always the result of clogged spray-arm jets and a dirty filter choking the water that scrubs them. Both clear in ten minutes with nothing but a toothpick and warm water. If a clean filter and open spray holes do not fix it, the usual next suspects are hard-water scale, wash water that never gets hot enough, and simple overloading, all covered below.
Causes, most likely first
| Cause | How likely | The fix | Typical cost |
|---|---|---|---|
| Clogged spray-arm holes | Most common | Pop off the arms and poke each jet clear with a toothpick or thin wire. Blocked jets kill the pressure that blasts food off. | Free |
| Dirty filter and food trap | Most common | Twist out the cylinder filter under the lower rack and rinse it under the tap. A greasy filter recirculates dirty water. | Free |
| Hard-water scale buildup | Common | White film and cloudy glasses mean mineral scale on the arms and heater. Run a descaler or citric-acid cycle. | $5–20 |
| Inlet water too cool | Common | Run the kitchen tap hot before starting, and set the water heater near 120F so the dishwasher fills at wash temperature. | Free |
| Overloading or bad rack layout | Occasional | Stop nesting bowls and blocking the spray arms. Water has to reach every surface, so leave gaps between items. | Free |
| Worn wash pump or seal | Rare | Weak spray after everything else checks out points to a tiring wash-pump motor. A tech tests and replaces it. | $150–250 |
Check these first
- Pull the lower rack and twist out the cylindrical filter. If it is greasy or packed with food, that alone explains poor cleaning.
- Spin each spray arm by hand and hold it to the light. Clear any jet you cannot see through with a toothpick.
- Run the kitchen sink until it is hot before you start the cycle, so the first fill is not cold.
- Look at your glasses. Cloudy, gritty film is hard-water scale; stuck-on food is a spray or filter problem.
- Reload with fewer, better-spaced dishes and rerun. Overcrowding blocks the water more often than people expect.
Prevent it next time
A dishwasher that cleaned fine a year ago and slowly got worse is telling you the filter and arms are overdue for attention. Rinse the filter on the monthly schedule, clear the spray jets while you are in there, and run a descaling cycle every one to three months if you have hard water. Setting your water heater to about 120F and using a rinse aid keeps wash temperature and sheeting where they need to be. Do that and most units clean like new well past their tenth year.
When to call a pro
Bring in a technician when a spotless filter, clear arms, hot water, and a descaling run still leave food behind, which points to a failing wash pump, a broken soap dispenser, or a bad water-inlet valve. Expect $90–150 for the diagnosis and $150–300 for a wash-pump or valve repair. On a unit past 10 to 12 years, weak cleaning is often the first sign the whole machine is winding down, and a replacement is the smarter spend.
Most of the causes above are maintenance problems wearing a disguise. OnOtto keeps the boring prevention on schedule so the 2 a.m. version doesn't happen.
Stop chasing symptoms, free for 30 daysFrequently asked questions
Should I rinse dishes before loading the dishwasher?
Scrape off bones and large scraps, but skip the pre-rinse. Modern detergents contain enzymes that need some food residue to grab onto, and spotless plates can actually come out worse. What matters far more is cleaning the filter and spray arms so the machine can do its job. Pre-rinsing also wastes roughly 6,000 gallons of water a year in a typical household, so a quick scrape is both cleaner and cheaper than rinsing every plate at the tap.
Why are my dishes covered in a white film?
A chalky white film is almost always hard-water mineral scale, not a detergent failure. Calcium and magnesium in the water dry onto glasses and the tub, and they also coat the heating element and spray arms until pressure drops. A rinse aid stops the spotting on the surface, but the real fix is a descaling cycle with citric acid or a commercial dishwasher cleaner every month or two. Homes on well water or in hard-water regions see this fastest.
Does water temperature really affect dishwasher cleaning?
It matters a lot. Dishwasher detergent enzymes and grease-cutting work best around 120F to 140F, and a fill of lukewarm water leaves fat smeared on dishes instead of dissolved. Because the dishwasher pulls from your hot-water line, running the kitchen tap hot for a few seconds first means the machine fills hot from the start rather than heating cold water mid-cycle. Setting the water heater to about 120F is the sweet spot for cleaning without scald risk.