How Do Dishwashers Actually Work

Dishwashers can be wonderful things. They can let you spend the evening relaxing with your family or friends, rather than tiring yourself out by scrubbing away at all those pots and pans you dirtied when preparing that tasty meal you all just shared. Just shove everything inside, add detergent, and switch it on. You are now free to go off to enjoy your evening.

But have you ever wondered how your dishwasher worked? 

Parts Of A Dishwasher

There are only a few major components to most dishwashers. While each model of dishwashers may have some variety as far as added features or how they work, each has the same basic parts. 


The tub is the main box of the dishwasher. It’s the water-tight compartment where all the cleaning takes place. This is usually well insulated to keep the heat in, and there will always be some kind of seal between it and the door to make sure water doesn’t leak out.

On a lot of machines the tub is made of stainless steel, while some are plastic. A stainless steel tub has the advantage of being more durable than a plastic tub. That may not be a requirement, since plastic tubs seem to last well in dishwashers that have them. But what a stainless steel interior allows is a hotter interior temperature, meaning the washer will clean with hotter water and may do so more efficiently than the plastic tub counterparts.

But that comes at a cost. A dishwasher with a stainless steel tub costs several hundred dollars more than one with a plastic tub. Stainless tubs can also show calcium deposits at times, which may require cleaning from time to time. This is less of a problem with a plastic tub.

Control Mechanism

This is the part that controls the timing of everything. A timer determines how long each part of the cycle lasts, then begins the correct functions at the appropriate time. This is what determines when the sprayers, drains, and detergent dispensers each activate. Some of these are computerized, but some are simple electromechanical timers. Most dishwashers require the door to be latched before they will activate, and some come with child safety locks.

Detergent Dispenser

Most dishwashers have two detergent dispenser cups in the door. One has a lid and one doesn’t. The one without a lid is for the pre-wash cycle, and it’s where you can add soap that will be immediately added during the initial pre-wash cycle. Your dishwasher’s control mechanism determines the correct time to open the door on the second cup, which occurs during the wash cycle. This is where the bulk of your detergent or your pod goes.

Inlet Valve

This is just an electrically controlled valve that opens to allow water from the home into the dishwasher. It’s like your sink faucet, except it’s controlled automatically by the control mechanism of the dishwasher.


The pump performs two functions in your dishwasher: it pumps water up through the spray arms and it pumps water out of the tub through the drain hose when it comes time to drain the dishwasher.

Spray Arms

Spray arms are where the water jets that clean your dishes are located. These arms spin around, forced into motion by the angle of the water jets. This helps them distribute the water evenly. A dishwasher may have one, two, or three of these arms, depending on the model. The most common design has one at the bottom spraying up and one at the top spraying down. There are some models with a third spray arm in the middle, usually spraying both up and down. 

Heating Element

The heating element is a small electrical heating tube in the bottom of the tub. The dishwasher heats the water in the basin up to the proper temperature before it is pumped through the spray arms while washing. Hot water typically cleans better, and most dishwashers heat the water to at least 140F.

Dish Racks

These are the wire racks where you place your dishes. Most dishwashers have an upper and lower rack, and both slide out like a drawer. The top rack is usually designed for glasses and small items, while plates and larger items go in the lower rack, where the machines have more room. There may also be a utensil basket that sits in the lower rack to hold your forks, spoons, and other utensils.

The Dishwashing Process

Now that you know what all the components are, it’s time to discuss how the typical dishwasher proceeds through the cleaning process. 

  1. Load The Dishes – The first step is loading the dishes into the dish racks. You’ll want to do this in the proper way, placing silverware into the utensil basket, glasses and cups in the top rack, and plates and pans in the bottom rack.
  2. Fill Detergent Cups – Now you can fill the main detergent cup (the one with the lid) with your detergent or pod. If there is a second cup, you can also add additional detergent at this time to add some soap to the pre-wash to help loosen some of the tough food deposits.
  3. Set The Wash Cycle – With some dishwasher models, you close the door, then set the wash cycle. Some models have the controls along the edge of the door, and you must set them before closing the door. Either way, set the controls and close the door at this point. The machine should begin running.
  4. Machine Fills With Water – At this point, your dishwasher will open up the inlet valve to allow water from your home’s water line to flow into the tub. When the water level reaches the correct level, the machine will then close the water valve.
  5. Heating Elements Warms Water – Now the heating element is engaged and the water in the tub is heated to around 140F. This can take a few minutes.
  6. Pre-Wash – In this phase, the pump of the machine begins pumping the hot water through the spray arms. This step is just a beginning rinse to loosen particles and spray a bit of hot water on the dishes to soften food deposits. If any detergent was added to the pre-wash cup in the door earlier on, much of it has already been dumped into the tub and mixed with the water at this point. If not, this spray will rinse it into the tub and it will mix with the water now. This extra soap can start a bit of the cleaning process before the main wash happens later on, which can help with especially dirty dishes.
  7. Main Wash – This is the cycle where most of the washing is done. It is when the main detergent cup in the door opens, allowing the remaining detergent or the pod to fall into the water and mix in. During this time, water is continually heated and the soapy water is sprayed through the spray arms and onto the dishes. The main wash cycle can typically take in excess of twenty minutes.
  8. Drain – When the main wash cycle is done, the heater will switch off and the pump will engage to pump all of the dirty water out of the tub.
  9. Final Rinse – During this cycle, clean water is pumped in and heated, then sprayed over the dishes again. This will repeat for several minutes to make sure the dishes are thoroughly rinsed.
  10. Dry – Your dishwasher may have a heated dry and/or an air-dry setting. If you select heated dry, during this cycle the dishwasher will pump hot air around your dishes and out a vent. If you choose the air-dry setting instead, the machine will blow room-temperature air across your dishes to aid in the drying process.

Types Of Dishwashers

There are a variety of different dishwasher types you may have around your home. There are also commercial dishwashers, which you usually find in places such as restaurants.

Standard Undercounter Built-In Dishwashers

These are the most common type of dishwasher, and the type you are most likely going to have in your home. They are permanently mounted under a countertop, usually in the kitchen, and have a water line from your home directly connected to them.

Most built-in dishwashers are 24 inches wide. It is the standard size that most homes have. Another size that you may come across is an 18 inches wide version. These are sometimes found in more compact kitchens or small homes. There are dishwashers wider than 24 inches, but they are not common.

Countertop Dishwashers

Countertop dishwashers are small dishwashers that do not need to be permanently mounted under a cabinet. They are usually small, since they are designed to sit atop your countertop, and usually connect directly to your sink. 

Most countertop dishwashers are usually from 16-22 inches wide and around 20 inches tall. Their much smaller size makes them popular in tiny homes, RVs, and small apartments. While they work in the same basic way as the built-in dishwashers, they have a much smaller capacity. They usually are quite a bit cheaper to buy than the built-in dishwashers.

Drawer Dishwashers

These mount under your counter, like a traditional built-in, but are designed a little differently. They are available as a single or double drawer setup, with many of the double drawer versions allowing each drawer to run independently of the other. 

These operate in the same manner as the typical dishwasher, with the exception that the whole unit comes out in a drawer for easy loading. They have most of the same features you find on other dishwashers, but these are quite a bit more expensive.

Portable Free-Standing Dishwashers

Portable free-standing dishwashers are full-size, or nearly full-size, dishwashers with an outer case and wheels. Some people consider countertop dishwashers to be portable, but these are different. They are designed so that you can roll them out of the way when not in use, then roll them out again when you need to use them. These are often a little smaller than a full-sized built-in dishwasher, but can be nearly as large or as large as a built-in as well.

These operate in the same basic way as a built-in model. The main difference is that when you need to use them you must roll them near the sink. You then run a pair of hoses, often bundled together, over to your sink to connect as a water source and so that your dishwasher can drain its used water into your sink, and ultimately down the sink drain.

Commercial Dishwashers

Commercial dishwashers are a bit different than household dishwashers. They can often wash a larger number of dishes at a time, and they typically wash dishes in a much shorter time. This allows them to run several loads per hour, which is something your home dishwasher won’t accommodate.

There are many different kinds of commercial dishwashers available, with some being very similar in size to a home system, and others being very large. Something you will notice if you are looking for a commercial dishwasher is that there are low-temperature and high-temperature models. 

High-temperature commercial dishwasher models usually heat all the water to a higher temperature, with the rinse cycle sometimes reaching as high as 180 F. This is to make sure the dishes are sanitized properly. They also often have a flash dry feature to help dry the dishes quickly when washing is completed. A downside to these machines is that they require a special condensate hood because of the steam they produce.

Low-temperature commercial dishwasher models use a chemical sanitizer to clean the dishes. They do not heat the water to a hot enough temperature to properly sanitize. Their normal heat is closer to a home dishwasher, somewhere in the range of 140 F. The low-temperature dishwashers don’t require a special hood to vent the steam like the high-temperature models, making them cheaper to install. While this does make them cheaper to install, you have the added ongoing cost of sanitizing chemicals. You also must scrape more of the thick food deposits from the dishes before placing them inside, since they do not clean large deposits as well as the high-temperature versions.

While most dishwashers operate in the same basic manner, you can see that they come in several different forms. Whether you have a countertop model or a built-in dishwasher, the main components are the same, and they can all save you a lot of time.

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