If your dishwasher can’t seem to clean, consider these five potential causes and how best to fix them
By Liam McCabe
Buying efficient appliances is one of the simplest, most effective ways to slash your household’s water use without really changing your lifestyle. But not everyone is thrilled with modern water-saving products, and eco-friendly dishwashers can be a particular point of ire.
Federal regulations for residential dishwashers date to the 1970s, though it wasn’t until this century that there was an obvious change in how dishwashers worked: In 2010, phosphates, key cleaning agents in dishwasher detergents, were largely removed from popular detergents due to their environmental impact. And dishwashers sold since 2013 can use no more than 5 gallons to wash a load of dishes, as measured by a standardized test. In the real world, that translates to 3 to 6 gallons of water per cycle, according to our tests, but either way it’s less water than nearly any hand-washing technique. Older dishwashers used to use around 10 gallons per load.
These new rules forced appliance makers to rethink the designs of their dishwashers. Some brands didn’t miss a beat and continued to produce high-performing dishwashers that made most of their owners happy. However, some people have found that the modern machines just don’t work as well as their old dishwasher did—at least one survey found that 75 percent of respondents said they pre-rinse their dishes.
What CR's Tests Reveal About Water-Saving Dishwashers
In our extensive lab testing, CR has found no clear relationship between a machine’s water use and cleaning performance: Some of the thirstiest dishwashers earn weak ratings in our washing test, while highly efficient models earn top marks.
Our cleaning test is intentionally challenging, and we have not yet found a dishwasher that can completely clean our test load.
Real-world messes tend to be easier to clean, though, and many dishwashers have no trouble washing away the crumbs, crusts, and grease from an actual real-world meal—even without pre-rinsing by hand.
CR members in the market for a new machine can see our ratings of more than 100 models from more than two dozen brands. Our Overall Score also includes data about reliability and owner satisfaction, collected from our surveys of CR members about more than 100,000 dishwashers used in real homes.
Reasons Your Dishwasher Can't Seem to Clean
Some people pre-rinse dishes out of habit, because their parents did, or because they used to with their old machine. If that is you, then at least try to skip the pre-rinse to see what happens—you have nothing to lose. If your dishes indeed come out dirty, here are possible offenders, and what to do about them:
A clogged filter: This can restrict the water flow in your dishwasher, so cleaning it should give the machine a performance boost. If your dishwasher has a removable filter (as most do), pop it out and rinse it under the faucet. Try to do this at least a few times per year, or whenever you notice a drop in your dishwasher’s performance.
Food and mineral deposits: These naturally accumulate throughout the system. To break them up, run a self-cleaning cycle: Leave the racks empty, add some powdered citric acid or a dishwasher cleaner, and run a heavy cycle. It’s wise to do this once a year, or whenever you notice chalky residue forming on the walls of your dishwasher.
An underperforming pre-wash cycle: Most dishwashers start loads by spraying tap-temperature water for 15 minutes to knock away loose soils (before opening the detergent tray and turning on the water heaters). You can make more out of the pre-wash portion—and boost the overall cleaning performance—by adding a microdose of powder or a splurt of gel detergent outside of the detergent door. Many dishwashers have a small notch on the detergent tray for this purpose, but you can also just add the dose directly to the bottom of the tub.
A subpar detergent: Detergents with enzymes in their formulas tend to outperform detergents without enzymes. (Most detergents do have them now, and it’ll usually say so somewhere on the packaging.) Beyond checking for that basic ingredient, see CR’s dishwasher detergent ratings to see the top performers and how more than 20 popular formulas handled our tough tests. Consider using a rinse aid, too.
Hard water: Hard water makes detergent less effective, so try softening it. Assuming you don’t have a whole-house softening system, or a dishwasher with a compartment for softening salts (these are uncommon), you could try using a hard-water “booster” product, or adding a small scoop of citric acid (the main ingredient in those boosters) to the tub or tray.
What to Do If Your Dishwasher Is, in Fact, the Problem
If you try all those steps and you still end up with dirty dishes . . . well, you’re out of options. Some dishwashers just don’t clean well, especially once they get to be a few years old. But remember, it’s not because they skimp on water—it’s because they’re lousy for other reasons.
If you’re stuck with a sub-par performer, there may be no escaping the pre-rinse. While CR generally recommends skipping the pre-rinse, some people with a poor-performing dishwasher have no other practical choice. To save water, pre-clean dishes by dipping them into a basin filled with a modest amount of cold water as opposed to running the water in your sink.
Water-Saving Dishwashers With Cleaning Power
Next time you buy a dishwasher, focus on getting one that can wash really well, because then you’ll be able to skip the pre-rinse—saving you time, money, and stress. Check CR’s dishwasher ratings to find a water- and energy-efficient dishwasher; most of the top performers in our ratings are Energy Star-certified. CR members can also find dishwashers that earn our Green Choice badge for sustainability.
Larry Ciufo, CR’s head of dishwasher testing, made a $100 bet with his mom that if she bought one of CR’s top-ranked dishwashers instead of a mediocre discounted model she wouldn’t have to pre-rinse anymore. He said he’d even hand-wash any dirty dishes if the new model failed to clean properly. She bought the better performer, and now her dishes come out clean every time without any pre-rinsing. “I won the bet—but I took a homemade dinner instead of the money,” Ciufo says.
Here are a few of our top overall performers to consider next time you need a dishwasher.
Consumer Reports is an independent, nonprofit organization that works side by side with consumers to create a fairer, safer, and healthier world. CR does not endorse products or services, and does not accept advertising. Copyright © 2022, Consumer Reports, Inc.