How Dishwashers Work

Using a Dishwasher

If your dishwasher isn't getting your dishes clean, you may not be loading it properly.
If your dishwasher isn't getting your dishes clean, you may not be loading it properly.
Photo courtesy DHD Multimedia

Even though the dishwasher does most of the work, humans play a part too. Here are some guidelines that can help your dishwasher operate safely, effectively and efficiently.

  • Don't use regular dish soap. The suds will overflow the dishwasher.
  • Don't overload the dishwasher. You need to leave room for the water jets to spray onto the dishes.
  • Face the dirtiest part of the dishes toward the spray jets, which usually come from the center.
  • Don't mix steel and silver items. Putting two different types of metal in contact in a humid environment is a perfect recipe for corrosion.
  • Try to keep bowls, spoons and other dishes with identical shapes separated. Otherwise, they will tend to nest together, and the water cannot reach every part of the dish.
  • Don't put wood, cast iron, fine china, crystal or hand-painted dishes into the dishwasher. Wash these items by hand.
  • Use the dishwasher at a time of day when water pressure is high, such as late at night. The dishwasher will clean better if you're not using a lot of water for something else, like washing clothes.
  • If your home has hard water, use slightly more detergent.
  • Use a rinse aid to avoid spots and help your dishes dry more quickly.
  • Don't put plastics on the bottom rack, especially if you use the hot drying cycle. The heating element could melt some plastics.
  • Don't pre-clean dishes. Dishwashers actually depend on the bits of food that cling to dirty dishes to maintain an appropriate ph level inside the dishwasher. Large pieces should be scraped into the garbage, though.


Detergent is an important consideration when running a dishwasher. Detergents counteract mineral deposits, or hardness, in the water. They contain solvents that help dissolve food, have abrasives that scour away stuck-on gunk and help food slide off dishes more easily. You can't use just any detergent in a dishwasher; only detergents specially formulated for dishwashing machines will work. Other detergents could damage dishes or generate so many suds that the dishwasher would overflow. Which detergent to choose – tablet, powder, or gel – is really based on personal preference. One type hasn't been shown to clean better than another type.

The problem most people encounter with dishwashers is a simple inability to get the dishes clean. There might be stuck-on food or residue from the detergent. A water pressure problem may be the culprit. You may need to replace the water intake valve. Another common problem is mineral build-up. If your house has hard water, the mineral build-up can clog the water jets. Clear each jet with a wire or pin, and run an empty load with some vinegar in the detergent dispenser about once a month.

Sometimes, the dishwasher has problems draining properly. There could be a clog in the drain hose, or a problem with the pump. It's also possible that the dishwater is getting too sudsy, and sensors in the washer aren't detecting the soap foam as water. This causes it to shut down the drain cycle too early. Just use less detergent.

Check out the next section for our dishwasher buyer's guide.