Do Dishwashers Use Hot Water Or Heat Their Own? – Temperatures Explained

Have you ever wondered where hot water needed for cleaning comes from in the dishwasher?

Do you need to turn on your water heater because if you don’t, the dishwasher will run with cold water?

We will talk right about it. You will find out whether do dishwashers use hot water or heat their own, what is the optimal temperature the machine needs to reach, what if the dishwasher doesn’t wash with hot water, and even more.

What Is Usual Dishwasher Water Temperature?

Most dishwashers clean at a temperature between 120 – 150 degrees Fahrenheit. This is the optimal temperature that is sure to clean your dishes. It’s important to note that usually, the lower ranges won’t actually sanitize your dishes.

High Temp And Low Temp Dishwashers

You can purchase a commercial dishwasher marketed as a high or low-temperature dishwasher. Both work in different ways. High-temp dishwashers work in a range of 150-180 degrees Fahrenheit while low temp dishwashers work in the above-mentioned range of 120-150 degrees Fahrenheit.


Temperatures In Different Cycles

Certain cycles will generate more heat than others will but not for the whole duration of the wash. Typically it’ll happen in the final rinse cycle of the dishwasher. so let’s explain how the dishwashing cycle works

  1. Pre-Wash And Rinse – Don’t do much cleaning. It’s the first burst of warm water that comes out of the spray arms and gets the dishes wet
  2. Main Wash – This is where the cleaning happens. The water is heated, sprayed, drained, heated up again, and sprayed. This goes on until the heating is switched off automatically. There’s no water left after the main wash is done.
  3. Final Wash And Rinse– A new batch of water is drawn in and begins the main wash process all over again.
  4. High Temp Wash – Heats the water during the whole wash process to at least 130 degrees Fahrenheit.
  5. Sanitize – Heats the water to 150 degrees Fahrenheit during the final wash.

So, Where Does The Hot Water Come From?

Dishwashers use a combination of heat coming from the sink’s water heater system and also use their own heating system. So to answer the question, they heat their own water but rely on a hot water line connection at the bottom of the sink to draw appropriately warm water inside. Energy-efficient dishwashers only rely on the heating element to heat the water.

Water Line

Your dishwasher should be connected to the hot water line under the sink. There’s a two-part valve under that you should connect to your dishwasher. Connecting your dishwasher to a cold water line can lead to pre-heater failure early on in the dishwasher’s life.

Hack: To speed up the process of heating water, you can turn on the sink faucet until hot water starts coming out so that the heating element inside the dishwasher has to heat less. With energy-efficient dishwashers, this is not as necessary.

Faucet Water Hack

Connecting A Dishwasher To A Hot Water Line

  1. Look for a hot water valve under the sink, it should have two valves one for the sink and one for the dishwasher. If the second valve is not present, you will have to install one.
  2. Take your dishwasher’s water line hose and screw it onto the valve
  3. Take pliers and tighten it
  4. Turn on the water supply on the valve

If you need to install a dishwasher in your kitchen, it’s easier to do so than you might think. This is just one part of it.

Heating Element

Located on the bottom of the dishwasher where the water enters. It’s not visible if you simply open the dishwasher but there are external heating element models as well.

Troubles In Paradise: Dishwasher Not Heating Water

You will know the problem is not heating properly if you notice some of these signs:

  • The dishes are crusty
  • Detergent residue on dishes
  • There’s food residue on dishes

Note: The dishes not getting cleaned properly can also be caused by you not loading the dishwasher properly.

The Probable Cause

Heating Element Broken – There are two types of heating elements. Open and flow through. The first one is exposed while the other one is hidden. The exposed element can stop working by simply something getting onto it. These elements are cheap to replace and it’s better to do so than to try and fix it.


Clogged Water Line – You might have a dishwasher that relies solely on your sink’s heating system to gather warm water. If that water line is clogged,  or simply closed, your dishwasher won’t get hot water in.

Thermostat And Timer Not Working Properly – This is a less common issue but dishwashers have a built-in thermostat and timer to know exactly when to release water. If the timer is set wrong or the thermostat can’t read properly, hot water won’t be produced

If you suspect any of the following, we suggest you call a professional to get to the cause and fix the issue.

Can You Run A Dishwasher Without Hot Water?

If the heating element of your dishwasher is broken, the dishwasher can use water heated by your water heater. But if the water heater is broken, too, then how can the dishwasher use hot water? It can not so it will use cold water. Yes, it’s possible but there’s a risk dishes won’t come out completely clean. Therefore, it’s better not to use the dishwasher before you make repairs.

To Wrap It Up

Basically, how your dishwasher heats water will depend on your type of dishwasher. An energy-efficient one will heat its own water and save you energy while some models don’t have a water heater built in and rely solely on the hot water line for hot water. Don’t connect your dishwasher to a cold water line though as it can damage the preheater.

As an English major student at the time, Petra was stuck at home with online classes when the lockdown started. Soon enough, Petra discovered a passion for cooking and making pastries to pass the time. She started small with some experimenting and trying out new techniques inspired by French, Italian, and Asian cuisine. Since then, she has become a full-blown “little chef”, making dinner parties for her friends and expanding her knowledge with cooking classes.