How Do Dishwashers Work?

Dishwashers are just about the handiest home appliance ever invented. Back in the college days I slaved over the sink washing dish after dish by hand because we did not have a dishwasher. You can put practically any type of dish in there (as long as it is dishwasher safe). You can even wash your retainer in there. A dishwasher can save you a tremendous amount of time and are sometimes taken for granted. Yet how do they work?

There are many brands of dishwashers, all with various special features. Some can hold more dishes than others while some are more energy and water efficient. Yet no matter who manufactures them, dishwashers all work using the same mechanics. So exactly how do dishwashers work?

Dishwasher Basics

A dishwasher is basically an automated robot that washes and rinses dishes for you. It fills itself with water, is automatically timed so that it uses detergent at the right time and drains the water at the right time. It can heat water for better cleaning results and can even heat the dishes to dry them. There are several sensors to control the operation. All you have to do is load the machine and unload it.

Despite what some believe, a dishwasher does not actually fill up with water. There is a small basin at the bottom where the water collects. A dishwasher is connected to your water supply and pumps in cold water when the first cycle starts. At the bottom of the dishwasher is a large electric heating element that heats the water. When the water is at the right temperature (somewhere between 90 degrees F and 140 degrees F) the pump send the water squirting out of holes in the sides and through holes in a spinning paddle at the bottom. The water is pressurized, kind of like a miniature car wash. The water mixes with the detergent and washes the dishes. As the water falls back into the basin, where it is heated and cycled through again.


Once the wash cycle is finished, the pump drains the dirty, soapy water out through the drain pipe. Then the rinse cycle starts. The operation is the same as the wash cycle except it doesn’t use any detergent. Water is sprayed out through the holes and spinning paddles to thoroughly rinse all of the dishes. When finished, the water is again pumped out through the drain.

The last basic cycle is the drying cycle. This doesn’t involve any water at all. The heating element at the bottom of the machine that normally heats the water comes on and heats the air inside the machine to dry the dishes.

There are some of the higher end models that come with extra features such as a garbage disposal. These disposals are used to eliminate large food particles from the dish water.

Energy Efficient Dishwashing

Some energy efficient dishwashing models are more energy and water efficient than others. The U.S. Government has a chart that gives the annual energy consumption of different models. This is a great way to shop and compare, especially if you are concerned about your utility bills. While dishwashers use more energy than handwashing, they definitely save on time spent washing and on the amount of water that is used.


Stronger detergents that would normally irritate the skin are used for dishwashers since they are automated and hands-free. These detergents may contain phosphates, bleaching agents, enzymes, and anti-corrosion agents. Most dishwasher detergents have a strong alkaline base. In recent years there has been the development of biodegradable detergents which are more environmentally friendly.

Dishwasher Tips

There are some odds and ends stuff that you should know about how dishwashers work such as things that you should and shouldn’t put in a dishwasher.

One of the most important things to remember is never use regular dish soap in a dishwasher. Just like in the movies, liquid dish soap will cause a huge amount of bubbles and suds to build up that will spill out from the dishwasher. Only use detergent that is specifically for dishwashers.

Never overload a dishwasher. A dishwasher needs space between the dishes so that the jets of water can reach every surface. If the washer is overloaded, then the water cannot get everywhere and the dishes do not get clean.

Never put crystal, wood, cast iron, or fine china in a dishwasher. These items can be damaged due to heat or detergents. Aluminum pans can be discolored and some metals, such as pewter, have a low melting point and may warp. Anything that is valuable or delicate should always be hand washed instead.

Also, you should never put plastic items on the bottom rack. By doing that it places the plastic items closer to the heating element and the item can melt.

When loading the dishwasher, load similar items together on the same rack. Put all glasses and cups together, dishes together, pot and pans together, etc. By keeping similar shapes together, the water can reach all the surfaces better.