How to Test Your Water Heater Thermostat

How to test a water heater thermostat

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A properly functioning water heater thermostat is crucial for efficiency, performance, and safety. However, thermostats can malfunction over time, leading to a lack of hot water or even dangerous situations. The good news is that learning to test a water heater thermostat is a relatively simple task that only requires a few tools and steps.

In this guide, you’ll learn everything you need to know about testing your thermostat to keep your water heater running smoothly – from how they work, to the tools you’ll need and recommended maintenance going forward. By the end, you’ll be able to interpret the thermostat’s condition and determine whether an expert eye is needed.

What Exactly Does the Thermostat Do?

Your water heater contains a thermostat that controls the temperature of the water inside the tank. This important component makes sure the water gets hot enough for household use, while also preventing dangerous overheating.

The thermostat has both an upper and lower element, each connected to a heating element. When the water temperature drops below the lower element’s setting (usually around 120°F), it will turn on the lower heating element. This heats the water. Once it reaches the upper element’s temperature setting (typically 140-150°F), that element turns off the lower heating element while the upper one maintains the desired hot temperature.

This back-and-forth dance between the upper and lower elements keeps your hot water supply right where it needs to be. The thermostat acts as the conductor, directing the heating elements to turn on or off based on the water temperature it detects.

Signs of a Faulty Thermostat

A faulty thermostat can compromise the performance and safety of your water heater. Here are some telltale signs there could be an issue:

  • Not enough hot water
  • Water that is too hot or cold
  • Heating elements staying on non-stop
  • Strange noises from the water heater
  • Rusty water

If you notice any of these warning signs, it’s a good idea to test the thermostat sooner rather than later. 

Example of water heater temperature controls before a test.

Gather Tools and Take Safety Precautions

The process used to test a water heater thermostat is straightforward, but having the right tools and taking some basic safety precautions will make the job easier and prevent any accidents.

You’ll need:

  • Multimeter for testing electrical continuity
  • Screwdrivers (Phillips and flathead)
  • Gloves and eye protection
  • Flashlight

Before Getting Started

  • Shut off power to the water heater at the circuit breaker
  • Turn off the water supply to the heater
  • Allow the system time to cool fully to prevent burns
  • Keep the area clear of slip hazards and don’t wear loose clothing

Having someone assist you is recommended, both for safety and convenience. They can hold a flashlight while you test with the multimeter and have an extra set of hands if needed. Take your time and don’t rush any steps. Testing the thermostat requires careful placement of the multimeter probes.

Testing the Water Heater Thermostat

Before starting testing, it’s helpful to understand how to interpret the results. A reading of 0 ohms from the multimeter indicates continuity and a properly functioning thermostat. This is what you want to see. If both thermostats show 0 ohms resistance, they are working correctly.

However, if one or both thermostats do not show continuity, with a high resistance reading or no reading, that points to a faulty thermostat requiring replacement. There would be a break in continuity that could impact temperature regulation. Now, you’re ready to go – just follow this process:

Locate the Thermostats

  • Refer to the owner’s manual to identify the thermostat location on your specific water heater model.
  • Remove the outer access panel so you can see the thermostats and wiring connections.

Testing the Upper Thermostat

  1. Disconnect the wiring from the upper thermostat terminals.
  2. Set your multimeter to the RX1 scale to test for continuity.
  3. Touch the multimeter probes to the upper thermostat terminals.
  4. Look for a reading of 0 ohms resistance, indicating continuity.
  5. If the reading is not 0 ohms, the upper thermostat will need replacement.

Testing the Lower Thermostat

  1. Disconnect the wiring from the lower thermostat.
  2. Follow the same process, testing for continuity across the lower terminals.
  3. You want the multimeter to again read 0 ohms.
  4. If the lower thermostat does not show continuity, it will also need replacing.

Reconnect all wiring securely once both tests are complete, and you’re finished!

Multimeter being used to test a faulty water heater thermostat element.

Other Recommended Maintenance

While testing the thermostats is critical, other maintenance tasks will help keep your water heater running efficiently and safely for years to come. First, draining and flushing the tank annually removes built-up sediment that can impact performance.

You’ll also want to periodically check and replace the anode rod, which protects the tank from corrosion. In addition, inspecting the temperature and pressure relief valve ensures it can operate properly to release excess heat or pressure if needed.

Finally, insulating older water heater tanks and connecting pipes can reduce standby heat loss and lower energy costs. Taking the time for these extra maintenance steps extends the life of your water heater and ensures it continues working as it should.

When to Call a Professional

There are certain situations where you may want to call in an expert to look at the water heater. If you encounter extensive corrosion, mineral deposits, or damage to parts that require replacement, it’s often best to let an expert handle the repair work.

Additionally, if the wiring connections are severely corroded or faulty readings persist after multiple testing attempts, professional expertise can properly diagnose and fix underlying issues. Calling in assistance is also a smart move if you feel uncomfortable working with the electrical components yourself. A professional has the skills and knowledge to safely troubleshoot more complex problems and ensure all repairs meet local code requirements.

While DIY maintenance can handle many tasks, knowing when it makes sense to bring in an expert is important both for safety and performance.

Final Thoughts

In summary, keeping tabs on your water heater doesn’t have to be a scary or confusing process. With this straightforward guide, you now have the key steps to test a water heater thermostat yourself using a multimeter. A few simple tools, basic safety precautions, and an understanding of how to interpret the results are all it takes to check continuity and catch any faulty thermostats.

While replacing some damaged parts is doable as a DIY project, we suggest calling in a trusted pro for any complex wiring or extensive repairs needed. If you have questions about your water heater or need expert attention to any area of your home, the pros with Fox Mountain Property Inspections are here to help. For homeowners in Maryland, Pennsylvania, Virginia, and West Virginia, reach out today!

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