Reliance Water Heater Thermostat Replacement

Reliance Water Heater Thermostat Replacement

This guide on Reliance Water Heater Thermostat Replacement will take you through: 

  • How do I know if my water heater thermostat is broken or bad?
  • 7 easy-to-follow steps to replace the thermostat on Reliance Hot Water Heater
  • How much does it cost to replace the thermostat?

Without further ado, let’s dive in. 

Table of Contents

How Do I Know If My Water Heater Thermostat Is Broken Or Bad?

Signs that will let you know about a bad or malfunctioning thermostat are: 

  • No hot water out of your water heater
  • Insufficient hot water that indicates the upper thermostat is at fault
  • The hot water recovery will become slow
  • The ECO button or reset button keeps tripping because of a bad thermostat 

But the best way to verify whether the thermostat is at fault or not is to inspect it electrically. The following procedure will help you check the thermostat electrically: 

Before the beginning of the test, turn the electric supply off to the unit at the circuit breaker.

Next, use a Phillips head screwdriver to unscrew the upper access panel. Fold away the insulation and pull out the thermostat protective cover. 

Fold away the insulation and detach the plastic cover
*Fold away the insulation and detach the plastic cover*

Note the orientation of the power wires and pull them out to isolate the thermostat from the circuit. 

Now, touch one lead of the multimeter to the left side terminal on the reset portion of the thermostat. And touch the second lead to the other left side terminal. 

The meter reading should be 0
*The meter reading should be 0*

The meter reading should indicate close to zero Ohms of resistance if the thermostat has continuity. 

The meter reading doesn't change significantly
*The meter reading doesn’t change significantly*

If the digital display doesn’t change significantly, I bet the thermostat has no continuity and it’s defective. 

Similarly, you can test the lower thermostat of the unit following the same method. If the thermostat has no continuity, you must replace that component. 

And the below chapter will help you make that replacement. 

Reliance Water Heater Thermostat Replacement [7 Easy Steps]

You will need the following tools and supplies near at hand when it comes to replacing the thermostat on your Reliance Electric Water Heater: 

  • A non-circuit tester
  • A replacement thermostat, which you can find in your local hardware stores or on big-box stores like Walmart, Home Depot, or Amazon. 
  • A business card to inspect the gap between the thermostat and the tank
  • A permanent marker and tape to mark wires
  • A Phillips head screwdriver

Safety Tips: Ensure you turn the power off. Otherwise, it will cause severe injury or even death from electrical shock if you work on an energized circuit. 

Once you have all the kits you need and take necessary precaution, follow the below step-by-step procedure to make the thermostat replacement. 

#1. Turn Off Electrical Power

Begin with turning the power off to the unit at the circuit breaker. From the top of the water heater, remove the electrical junction box. Then, check the power wires with a non-contact circuit tester to ensure the power is off. 

#2. Unscrew the Upper or the Lower Access Panel

Removed the access panel, insulation, and the plastic cover
*Removed the access panel, insulation, and the plastic cover*

Use the Phillips head screwdriver to unscrew either the upper or the lower access panel. It depends on what thermostat you are going to replace. Afterward, take the insulation out and remove the thermostat plastic cover to expose the thermostat. 

#3. Remove Wires From The Thermostat & Pull Out It

Pull out the wires from the thermostat.

Removed the wires and marked them so that back those wires on correctly
*Removed the wires and marked them*

Before doing so, mark the wires using the tape so that you can back them on correctly.

Next, remove the thermostat from the metal mounting clip. 

#4. Install The New Thermostat

After removing the bad thermostat, it’s time to install the new thermostat. Verify the replacement thermostat matches the original thermostat. Also, make sure the thermostat fits snugly against the tank. 

Use the business card to ensure you install the thermostat tightly against the tank. If you can slip the business card between the thermostat and the tank, understand the thermostat doesn’t fit snugly. 

In this case, keep bending the thermostat mounting clip until the thermostat fits tightly against the tank. 

#5. Reattach the Wires

After completing the thermostat installation, reattach the wires you detached earlier to the thermostat. If needed, check the wiring diagram on the water heater’s label and connect the wires according to the wiring diagram. 

#6. Replace Everything Back Into Place

Now, put everything like the thermostat plastic cover, insulation, and access panel back into place. Also, replace the cover on the electrical junction box. 

#7. Restore The Power

Finally, restore the electric power to your water heater at the circuit breaker. It will take at least two hours for the tank to heat up. 

How Much Does It Cost To Replace A Water Heater Thermostat?

It will cost you at least $150 to $200 to replace a water heater thermostat professionally while the part itself is less than $25.  

Fortunately, you don’t need to hire a professional to make that small replacement. Just follow the step-by-step procedure I mentioned and have the thermostat replaced successfully. 

In short, you can save up to $100 if you make the replacement by yourself.


Are thermostats for hot water heaters universal?

No, thermostats for hot water heaters are not universal. So, bring the old thermostat with you when shopping for a new thermostat in your local hardware store. On the other hand, note the part number on the thermostat if you order the replacement part online like on Amazon.

Do you have to drain the water heater to change the thermostat?

No, you don’t need to drain the water heater to replace the bad thermostat with a new one.

How long should a hot water thermostat last?

A hot water thermostat will last around 6 to 12 years.

What happens when a water heater thermostat goes out?

You will get not or not enough hot water if the thermostat on your water heater goes out.

Can you fix a water heater thermostat?

The only way you can fix a water heater thermostat is to replace it with a new one if it gets defective. On the other hand, if the thermostat is in good condition, ensure the wires attached to it are tight and secure.


Replacing a thermostat on Reliance Electric Water Heater is simple. Just follow the 7 step-by-step procedure I broke down and get your thermostat replaced successfully. Happy Plumbing!

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