Dishwashers are essential kitchen appliances designed to save you water and energy. Knowing that they remove grime and germs better than hand washing, you may wonder if your dishwasher heats its water to sanitize it.
Almost all dishwashers heat their own water. The appliance can heat the water in a basin or run it through a flow-through heating element. Most dishwashers connect to a hot water line that pulls hot water from the home’s water heater, then they further increase its temperature to 130-140°F, for cleaning and sanitation.
How Does A Dishwasher Heat Up Water?
Dishwashers have either a visible black metal ring on the bottom or a hidden flow-through heating element.
Generally, the dishwasher’s plumbing connects to the kitchen sink’s hot water line, enabling the appliance to pull in hot water (although some plumbers may connect it to the cold water line).
A temperature gauge detects the water temperature and activates the heating element to bring it up to 130-140°F for cleaning.
The temperature gauge and a control timer also monitor the temperature during the cycle.
Dishwashers are not filled to the brim with hot water. Instead, water is pulled into the basin and heated up.
The machine then adds a cleaning agent to dissolve in the hot water. This mixture is pumped and sprayed around the interior.
You will hear the water drain at some point during the cycle, and then the heating process takes place again. This time it is without the cleaning agent, to rinse off any remaining residue.
For the final rinse, the National Sanitation Foundation requires that residential dishwashers reach a minimum of 150º F.
Many dishwasher models offer a heat dry option for the cycle. The heating element works to heat dry the dishes after all of the water has been drained away. Some models use hot air drying instead of the heating element.
Read on to learn more about how dishwashers get hot water and what you can do if it is not working.
Types of Heating Elements
Basin Heating Element: Visible
This heating element is easy to find in your dishwasher basin, underneath the bottom spray arm and shelf.
It looks like a metal ring with clamps holding it in place. However, LG and Miele dishwashers will have one that is tong-shaped, with elongated loops.
The basin collects water and heats it with the heating element. The machine then pumps the water forcefully around the inside to wash the dishes.
Brands that offer visible heating elements include Whirlpool, GE, Frigidaire, Kitchenaid, LG, Miele, and Maytag.
Minerals from hard water can stick to the heating element. Over time, you can see scale deposits that build up on it.
If plastic items fall to the bottom of your dishwasher, the heating element could melt them. These issues can affect its functioning but are easy to clean to ensure the heating element is working at its full capacity.
If the heating element is damaged or fails to work, you need to replace it.
Flow-Through Heating Element: Hidden
The flow-through heating element is hidden inside the lower housing of the machine. It is a channel or tube-like part that heats water as it travels through it.
Hot water pools in the basin, then it is pumped and sprayed around the machine to clean the dishes.
Brands that offer the flow-through heating element include Bosch and Asko.
This heating element could build up limescale over time and need cleaning. The appliance will need to be taken apart to access it.
This video demonstrates how to replace a dishwasher flow-through heating element:
6 Reasons Why The Dishwasher Doesn’t Heat Water
If your dishwasher is not using hot enough water, you may notice food that remains on the dishes, soapy residues, or that the dishes are cool to touch right after the cycle has finished.
There are several reasons why your dishwasher doesn’t heat the water, as outlined below.
1. The Heating Element Fails
Clean the heating element to remove food, limescale, or melted plastic. Replace the heating element if it still does not work, or investigate further to determine if another part is malfunctioning.
2. Malfunctioning Internal Thermostat or Control Timer
The internal thermostat, or control timer, tells the heating element when to turn on during the wash cycle.
A service professional can investigate this problem by checking the voltage with a multimeter.
If you choose to do this check yourself, follow safety precautions to avoid electrocution. Refer to your user manual to open the dishwasher housing and the directions for using a multimeter.
3. Malfunctioning Water Tank
Generally, water tanks in homes heat water to 120-180°F. However, homeowners commonly set the tank to 120°F to avoid scalding.
If the water coming into the dishwasher is cold, then your dishwasher’s heating element has to use more energy and may struggle to get it to the required temperature during the cycle.
Check your water tank to see if it is the root of the problem:
- Electric Water Tank: Electric water tanks could have blown fuse or tripped main circuit breaker. Replace the fuse and check the circuit breaker. This kind of water tank may also have a safety circuit near the thermostat that needs to be reset.
- Gas Water Tank: Gas-powered water tanks have a pilot light that has gone out or there is a problem somewhere in the gas line. Call in a professional to deal with any gas equipment for your safety.
- All Water Tanks: Water tanks can have other issues as well that affect their functioning.
- Set the thermostat at a minimum of 120°F. Run hot water from a tap and test it with a thermometer to make sure it is working.
- A service professional can look over your water tank for any malfunctioning parts and check the pressure relief valve to ensure it is working.
- Sediment can build up and a service professional can flush it out to prevent corrosion.
- If the water tank is leaking water or has too much corrosion, it will need to be replaced.
4. Hot Water Pipe Inactivity
When the dishwasher is not being used, water sits in the pipes, cooling down. So, the water coming into the dishwasher at the beginning of the cycle is cold.
The heating element can warm up the water, but it takes longer and consumes more energy.
Sometimes, the water may even be too cold for the dishwasher to heat up fast enough during the cycle.
If you notice this to be a problem, you can bring hotter water to the dishwasher at the start of the cycle by turning on the hot water at the sink first.
Then, the dishwasher only needs to heat the water as necessary for the model’s wash cycle requirements, using less energy and becoming more efficient.
Interestingly, hot water that travels in pipes through uninsulated concrete slabs, basements, or crawl spaces, can cool down several degrees.
If your dishwasher model needs a minimum of 120°F, then it may struggle to fully heat the water if it is reaching the dishwasher lower than this.
To remedy this, turn your hot water tank up by ten degrees, to 130°F. Make sure you use caution for showering and washing your hands to avoid scalding water.
Another option is to run hot water into a cup in the kitchen sink. Place a kitchen thermometer in it. Once it reaches 120°F, you can turn on your dishwasher.
5. Large Demand For Hot Water
If you run the dishwasher and someone in the home is also taking a hot shower, there may be too large of a demand on the water tank to supply hot water.
As a result, lukewarm or cold water is delivered to the dishwasher or the person showering.
To remedy this, run the dishwasher only when no one else is using hot water.
6. Poor Maintenance
The dishwasher won’t function properly if it is not maintained. Refer to the user guide for your brand of dishwasher and maintain it to increase its longevity and cleaning efficiency.
In general, you should do the following:
- Clean or replace the filter to remove food particles and clogs.
- If your dishwasher is connected to the plumbing for your garbage disposal, the disposal should also be maintained. Flush out grease and clogs.
- Use a dishwasher cleaning tablet or Calcium-Lime-Rust (CLR) cleaner to break down and wash away mineral deposits from the heating element, spray arms, and interior.
- You can also put a cup of vinegar upright on the top shelf and run a cycle to loosen and wash away debris.
Do dishwashers heat cold water?
Dishwashers can heat cold water, and you can run a dishwasher with cold water.
However, it is likely your dishwasher will try to use a lot of energy to heat it, and it may not reach the required sanitation temperature of 150º F for the final rinse cycle.
How long does a dishwasher take to get hot?
On average, it takes approximately two minutes for a dishwasher to heat the temperature by one degree.
Your dishwasher will reach its required temperature faster if you run hot water at the connecting kitchen sink first.
Dishwashers use a heating element to heat water from the hot water line to effectively clean and sanitize dishes.
The final rinse cycle must be a minimum of 150º F, and this temperature is hard to achieve if the water feed is cold.
If the dishwasher is not heating up as needed, there may be a problem with the heating element, the plumbing, the hot water tank, or other parts of the appliance.
Contact a service professional if you cannot find the source of the problem and fix it yourself.