Why Is My Water Heater Suddenly Getting Too Hot?

Last Updated On July 14, 2024

Updated on March 30, 2022



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water heater too hot how to adjust temperature

Is your water heater suddenly scalding hot? Learn why your water heater may suddenly cause your water temperature to get too hot and how to troubleshoot excessively high (and dangerous) water heater temperatures. 

In this PlumbingNav guide, we will cover:

  • Optimal Water Heater Temperature 
  • Problems Caused By Excessively High Temperatures
  • Common Causes For a Suddenly Too Hot Water Heater 
  • How to Fix Scalding Water Heater

What's In This Guide?

      Optimal Water Heater Temperature 

      You want your water heater to provide hot water that doesn’t get to the point of scalding. To prevent this, the U.S. Consumer Product Safety Commission (CPSC) recommends not to set your water heater higher than 120°F.

      Most installers set new water heaters to a default temperature of 120°F. While you can raise the temperature on many models to 140°F or higher, especially models designed for commercial use, most manufacturers include features to keep the unit set to a safe temperature. 

      Problems Caused By Excessively High Temperatures

      Water heater temperatures that are too hot can result in dangerous conditions for you and also damage to your unit. These are the top problems caused by water heaters with excessively high temperatures. 


      If you allow hot water from your water heater to touch your skin at high temperatures, you may burn yourself. The higher the temperature and the longer you keep your skin underneath the water, the more severe the burn. For example, 140°F water can burn you in only five seconds.

      Avoid Your Water Heater Becoming Suddenly Scalding Hot

      It takes substantially more energy to heat water to a higher temperature, especially if you have a tank-style unit. Whether you have propane, natural gas, or an electric water heater, you will pay more in utility bills when your water heater generates excessively hot water. 

      When set to 140°F instead of 120°F, your water heater will waste up to $61 annually in standby heat loss and $400 in direct consumption. 

      Faster Deterioration of Water Heater 

      Higher water temperatures lead to more sediment buildup and expedited corrosion in your water heater. These actions will cause the tank to deteriorate more quickly than if the unit runs at a lower temperature.

      Common Causes For a Suddenly Too Hot Water Heater 

      Why is your water heater suddenly scalding hot? When your water heater overheats, you need to diagnose the source of the problem. Consider these common causes for suddenly “hotter-than-normal” water heater temperatures. 

      Temperature is Set Too High 

      Too hot water temperatures can derive from an improper setting. This can happen at installation, or if a family member made an adjustment for a hotter shower.

      Check the temperature of your water heater to ensure it doesn’t exceed 120°F. If at a higher setting, follow the necessary steps for your hot water system to change the temperature on your heater. 

      Damaged Pressure Relief Valve

      If the pressure relief valve becomes damaged, hot steam can develop inside of the water heater tank. The hot steam will create hotter water. You can recognize a faulty pressure relief valve by checking or these possible issues: 

      Mineral Sediment Buildup

      If sediment buildup develops in your water heater tank, it can cover the heating elements, forcing them to work overboard. This can overheat the water in your water heater. 

      You can tell if you have mineral sediment buildup when you notice a popping noise coming from your water heater. To prevent sediment buildup, consider buying a water softener.

      did you know water heater too hot

      How to Fix a Water Heater That Is Too Hot Or Overheating 

      The solution to scalding hot water temperatures varies based on the cause of the problem and the type of water heater in your home. Use these steps to reduce unreasonably hot water temperatures. 

      Gas Water Heater Too Hot: Steps to Fix

      Your gas water heater uses a burner to heat the water in the tank. The burner activates whenever the thermostat comes into contact with water lower than the temperature setting. When something disrupts this process, you may notice high water temperatures. 

      Use these tips to fix a gas water heater when it gets too hot: 

      1. Set Temperature

      Find the gas valve. This will also have a dial for the temperature setting. Ensure you have the unit set to your desired temperature. 

      1. Flush Water Heater

      Flushing your water heater will remove the sediment buildup around the heating element. Flushing the water heater consists of draining the water heater tank and refilling it back up with water. Continue the process until you no longer see sediment in the water.

      1. Replace Damaged Components

      Sometimes the water temperature gets too hot due to a faulty component. The three components that may possibly cause the problem are the thermostat, heating element, or pressure relief valve. If your water heater is too hot then cold, test the thermostat or heating element.

      Electric Water Heater is Too Hot: How to Remedy

      Your electric water heater uses an electric burner to activate the heating elements. If you have an issue, start by turning off all power to the unit before assessing, as a safety precaution. 

      Use these steps to resolve the problem when your electric water heater generates water at excessively high temperatures. 

      1. Set Temperature

      To set the temperature on your conventional electric water heater, you will need to find the temperature control behind the access panel. The temperature control can come in the form of a dial or a digital control panel. Check the temperature and lower it if necessary, 

      1. Test Thermostat

      Test the thermostats in your water heater to verify proper function. Keep in mind that most home water heaters use a dual-heating design, meaning you will need to test both thermostats. 

      1. Reset Water Heater

      Many issues with electric water heaters involve malfunctioning thermostats. Find the red reset button on your unit and reset it to see if that resolves the problem. 

      1. Replace Faulty Thermostat

      If the reset does not resolve the issue, you will need to replace the faulty thermostat. See the video below to learn how to easily replace the faulty thermostat yourself.

      Tankless Water Heater is Too Hot: What to Do

      Tankless water heaters produce instant hot water instead of storing hot water in a tank. When the water gets too hot, you should try the following tankless water heater troubleshooting steps for a more optimal hot water temperature. 

      1. Set Temperature

      In most cases, tankless water heaters will have a digital control panel to make setting the temperature easy. Check the digital temperature display and change it to the desired temperature if set too high. 

      Some tankless water heaters even come equipped with smart features that allow you to control the temperature from an app on your smartphone. 

      If you see a diagnostic code on the display, use the owner manual to learn what it means. 

      1. Tighten/Replace Temperature Sensors

      The sensors tell the thermostat when to generate heat. If the sensors don’t communicate with the thermostat properly, it can lead to high water temperatures. 

      If the water still gets too hot after adjusting the temperature, you may need to locate the temperature sensors and tighten them. If tightening the sensors doesn’t work to fix them, you should replace the sensors. It’s a good idea to check them periodically while performing maintenance.

      1. Wash Inlet Filter

      Your water heater’s inlet filter located at the cold water supply requires annual cleaning. This device protects your uint from scale, but it won’t work properly when dirty. You can clean it when you flush the water heater by running it under a faucet or using a cotton swab. 

      Quick-Read FAQs For Too Hot Water Heater

      Why is my hot water getting too hot?

      The main reasons your home’s hot water gets too hot include:

      • Improper water heater settings
      • Sediment buildup on heating element
      • Damaged pressure relief valve

      How do you know if your hot water heater is overheating?

      To find out if you have an overheating water heater, check the temperature setting on the device. You can also use a thermometer at your hot water faucet. You should reduce any temperature over 120°F. 

      What happens if a hot water heater overheats?

      If your hot water heater overheats, you may experience burns on the skin, low-efficiency levels, and increased deterioration of your water heater. 

      If caused by a damaged pressure relief valve, it can even lead to an explosion. To avoid this rare but dangerous situation, make sure to look for the warning signs of suddenly hot water and other issues.

      What do I do if my water is too hot?

      If your hot water heater is water heater suddenly scalding hot, you check the temperature on the thermostat, flush the unit, and replace any faulty components. Keep in mind that different unit types may have slightly different procedures.

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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