How Does a Dishwasher Heat Water: what you didn’t know

Last Updated on April 7, 2022 by

How does a dishwasher heat water? Whether you want to fix it or are just curious about how your dishwasher heater operates, this publication provides the needed explanation. We would also consider the major wash cycles that kick in.

A dishwasher contains a heating element that heats water to 130-140 degrees Fahrenheit depending on the selected wash cycle/program or dishwasher model. Some dishwashers also feature built-in sensors that tell when the water level reaches its capacity.

Here is a tip: before you start the dishwasher, run hot water from the kitchen sink to the dishwasher. This starts the wash cycle with hot water, so your machine will not have to consume further energy heating the water (if it has a built-in heater).

Read also: should you buy a convertible built-in dishwasher?

How does a dishwasher heat water?

A dishwasher needs hot, or at least, warm water to clean and sanitize dishes. The dishwasher heats water to temperature levels of 130° F-140° F, or more, depending on the model. Also, a dishwasher that heats features a heater.

Water is not heated immediately since your dishwasher draws it from the sink supply lines through external connections.

When you start a wash cycle, the bottom pool of your dishwasher receives the water. This water is heated by a heating element at the bottom of the machine.

The water mixes with the dishwasher detergent and moves to the spray arms, which are at the top and bottom of the machine, and occasionally below the leading rack.

The hot water rises through the spray arms to the dirty dishes, where stains are eliminated. Occasionally, the cleaning water returns to the pool to filter, reheat, and returns to the spray arm for cleaning.

Dishwashers are designed to use the same water to conserve water. Whenever the water reaches the specified temperatures, the sensors disable the heating unit.

The pumps, however, keep pressing water through the spray arms. After the wash cycle, the dishwasher drains the used water for a new one used for the cycle.

Why is it better to use hot water in a dishwasher?

The trick to minimizing cycle time is to run the hot water faucet from the sink to the dishwasher. This reduces the time and energy the dishwasher uses to heat the water itself.

Whirlpool confirms that your dishwasher pauses 2 to 3 times during a cycle to heat the water to the required cleaning temperature.

When the water heater reaches the needed cleaning temperature, the cycle advances.

Below are the advantages of plumbing hot water to the dishwasher when the cycle begins:

  • Get rid of the need for long heating pauses.
  • Reduce the time it takes to complete the cycle.
  • The dishwasher takes less electrical energy, saving your bills.

The water should reach 120°F when entering the dishwasher for optimal performance. Although your dishwasher can use cold water, dishes may not wash enough at low water temperature.

Also, the water cannot be too hot. Otherwise, some soils will be harder to remove and certain detergent ingredients will malfunction due to the high temperature.

Read also: out recommended detergent for Bosch dishwashers

Dishwasher wash cycles

This section explains the various wash cycles:

  1. Pre-rinse

Pre-rinse is the first initial warm water burst through the spray arms to wet the dishes for a few minutes. This cycle does not make your loads clean, it only prepares them for the main cycle.

On some dishwasher models, you get a pre-wash cleaning agent dispenser for adding additional cleaning power for pre-rinsing.

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Pre-rinse is not always advisable if water conservation is your priority. You could simply scrape off the food and start the main cycle.

  1. Main wash

The main wash cycle handles your greasy dishes to make them cleaner. The main wash can take 20-60 minutes or more depending on the cycle/program you select.

During this cycle, water is heated, sprayed, filtered, and sprayed continuously, during which the heating system turns off whenever it reaches the temperatures.

Finally, the dishwasher drains water after the primary wash.

  1. Rinse cycle

When the rinse cycle starts, your machine draws new, clean water which is heated, sprayed, filtered, and reheated for the rinsing. The heating element turns off and on again whenever the wash cycle is reached.

The rinse cycle may no longer use a cleaning agent like pre-rinse (in some models) and wash cycle.

The drying stage

At the end of the cleaning cycles, additional drying may kick in depending on your dishwasher model, including the heated dry, condenser, or air dry. If the dry options will not dry your dishes, here are the things we did to fix our wet dishes.

The dishwasher may also engage a unique storage system that stores the loads for several hours.

  1. Condenser

Condensing dry is an innovative drying technology that combines a fan and the heat generated from the final rinse cycle to dry your dishes.

This technology is energy efficient and uses the remnant heat from the final rinse cycle. It does not damage cabinets or countertops compared to traditional venting that emits hot steam.

Condensing dry is much quieter since it redirects and dissipates moisture to the dishwasher base instead of filling the room with it.

  1. Heated dry

Heated dry uses a unique heater for fast drying for about 30 minutes on most models. However, heated dry consumes more power, and should be used sparingly.

  1. Auto air

Auto air in some dishwashers is designed to dry dishes by automatically opening the door after or during the final minutes of the cycle.

Normally, the dishwasher door opens when the temperature falls below 122 degrees Fahrenheit, depending on the model.

Fresh air circulates within the dishwasher, and an internal fan may activate to protect the machine from moisture.

Air dry is energy efficient but takes longer than condensed and heated dry. Since this is an efficient feature, most manufacturers enable it by default but can be turned off by the owner when necessary.

We have reviewed the best auto air dry dishwashers here.

Best dishwasher with heating element

Regarding how a dishwasher heats water, we recommend this one dishwasher with an energy-efficient water heating system:

Danby DDW621WDB Countertop Dishwasher with 6 Place Settings, 6 Wash Cycles and Silverware Basket, Energy Star-Rated with Low Water Consumption and Quiet Operation

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Danby DDW621WDB comes with the following:


This is a 6 place setting and 11.7-liter dishwasher with a silverware basket. For its compactness, a decent capacity.


Not the quietest but 52db is below normal human conversation. It ensures the ambiance in your small kitchen, RV, boat, or dorm. This is how we make our reviewed dishwashers operate silently.

6 wash cycles

The wash cycles include intensive, normal, rapid, economy, soak, and glass. The economy cycle is perfect if you care about your environment, efficiency, and economy.

Delay start

Danby DDW621WDB features delay start functionality. We were able to conveniently schedule our wash by 2, 4, 6 to 8 hours.

What we like


This machine is built with a durable stainless steel interior.

Water input turns off by itself

The water input will turn off by itself after the dishwasher turns off. However, taking off the hose will, of course, turn off the faucet.

Baby bottles

Danby confirmed that we could wash baby bottles in this model.


This dishwasher weighs just 46.30 pounds, light enough for any tabletop.

Read also: Gas grills need briquettes?

What we don’t

No adapter if your sink has no threads

Danby has a single type of adapter that requires threads either on the outside or inside of the tap.

Drying dishes

This dishwasher tries to dry your loads. However, we found that the loads will not completely dry.

The trick is to open the dishwasher door after the cycle for steam to exit the cabin. Danby also owned up to admitting that this dishwasher is not a great dryer.

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Why is my dishwasher not heating the water

If your dishwasher will not heat water, below could be the problem:

  1. Faulty thermostat

A faulty thermostat will keep your dishwasher from heating water for cleaning the loads since it regulates the water temperature in a wash cycle.

Thus, your dishwasher will not be able to tell when to disable or enable the heating element to ensure the water remains at the required cleaning temperature.

  1. Dead heating element

Notwithstanding whether your dishwasher is plumbed into a hot or cold water supply, many dishwashers use a heating element.

The heating element is visible in the tub and controls the water temperature from cold to hot. In some models, it helps in the heated dry process after a cycle.

The heating element may be a reliable dishwasher component but can burn out.

  1. Plumbing to the cold water line

You want to be sure that the dishwasher is not receiving cold water from the water line. Suppose your dishwasher has no internal heater and receives cold water from the water line. Not a chance it can heat without the element.

Make sure you are getting hot water into the dishwasher for the dish cleaning to complete with a squeaky outcome.

  1. Using a dishwasher with cold water

Using cold water in your dishwasher will not damage it. However, the dishwasher will not fight stubborn stains and grease with cold water, irrespective of the dishwasher detergent or pods you use. The pods will not even dissolve.

Meanwhile, Bosch recommends that you connect your dishwasher to cold water “unless you have an energetically favorable means of generating energy from a suitable installation”. This includes a solar heating system with a circulation line.

This applies if you intend to send hot water to the dishwasher to reduce the dishwasher heating time.

Have in mind that you need a dishwasher with a heat pump to regulate the water temperature based on the wash cycle or program that you select. Otherwise, you would be stuck on a one-way wash cycle, which can quickly degrade your dishes and kitchen utensils.