Rheem Marathon Water Heater Problems

Rheem Marathon Water Heater Problems

This guide on Rheem Marathon Water Heater Problems will walk you through 6 common water heater issues, including: 

  • Generate black sooty particles
  • Leaking
  • Heating elements problem
  • A popping noise coming from the pressure relief valve
  • Not heating
  • Water too hot

Table of Contents

Rheem Marathon Water Heater Problems [6 Problems & Their Solutions]

Let’s go through the troubleshooting steps straight. 

1. Generate Black Sooty Particles

Sooty particles coming from Rheem Marathon are a problem some users encounter. It actually comes from the flex lines running from the tank to the water heater. 

What actually happens is- the chlorine in the water eats up the rubber in the existing hoses and produces black soot particles, which you get from the water heater.  

How To Fix: 

You can easily get rid of this issue by replacing all the existing lines with flexible copper, which is long-lasting as well. 

Or, you can try these 100% stainless steel water heater connectors to connect the unit to the tank:

2. Leaking

Leaking is also a problem most Marathon owners go through to some extent in their usage. 

Here are some suspicious points on your water heater from where water may often leak: 

  • Damaged drain valve
  • Pressure relief valve
  • Heating elements (the seal of these elements often get corroded)
  • Crack in the tank

How To Fix: 

Inspect all the areas that are prone to leak and fix them. For example, if the water heater leaks from the drain valve, you must replace it. On the other hand, you must call a certified plumber right off the bat if you suspect the water is leaking from the tank. 

Fortunately, we compiled an in-depth article on Rheem Water Heater Leaking. Check out that article to learn everything you need to know about leaking. 

3. Heating Element Problem

The problem with the heating element is one which prevents the unit from heating water. Over time, the minerals contained in your supply water build deposits on the heating elements. 

As a result, the heating element loses its efficiency and fails to produce hot water. 

Another insight is- you will hear a rattling or rubbing noise from your water heater if the buildups form on the heating element. 

How To Fix: 

Cleaning or replacing the heating element is a simple fix to this issue. To clean the heating elements, follow the below step-by-step procedure: 

  • Turn off the water supply to the unit by flipping down its circuit breaker.
  • Unscrew the upper panel with the help of a Phillips head screwdriver. Remove the plastic protective cover as well as the insulation.
  • Pull out the wires from the heating element. 
  • Now, get an element wrench and remove the heating element. Don’t forget to put a bucket under the heating element as the water can drain from it. 
  • Once you remove the heating element, clean the deposits that form on it.
  • After cleaning the heating element, reinstall it back into its place. 

Don’t hesitate to replace the heating element if cleaning this component doesn’t bring any luck. Follow the same procedure to clean or replace the bottom element as well.

4. Popping Noise Coming From Pressure Relief Valve

Thermal expansion in a closed system builds up pressure and the noise you hear from the pressure relief valve is the by-product of it. 

How To Fix: 

This problem is not acceptable and you must correct it. I highly recommend you call a verified plumber to let him correct this issue professionally. Of course, never plug the pressure relief valve when this problem occurs. 

5. Not Heating

Your Rheem Marathon Water Heater is not heating due to one of the following reasons: 

  1. The tripped circuit breaker or the fuse gets blown out
  2. Electric supply to the unit may be off
  3. Improper wiring
  4. Manual reset limit
  5. Defective heating elements
  6. Too low thermostat setting
  7. Leaking or open hot water faucets
  8. Electric service to your home may be interrupted 
  9. Water usage demand may have exceeded the capacity of the water heater
  10. Colt water inlet temperature may be colder during winter months 

How To Fix: 

1. Check the circuit breaker for the water heater. If it gets tripped, reset it by flipping it to the Up position. Alternatively, replace the blown-out fuse if you use it to install your water heater. 

2. The electric supply to your water heater will be off if you don’t plug it into the outlet. Regarding this, what you need to do is- plug the power cord into a standard outlet. 

3. Call a certified plumber to examine the water heater wiring and allow him to wire the heater according to the manual and local codes. 

4. Every electric tank water heater from Rheem has an ECO or reset button. When the water temperature exceeds the safety level, this button will trip and cut off the electric supply to the unit. 

Just reset that button and it will solve the issue. You can locate it on the upper thermostat. To access the button, remove the upper access panel and pull out the insulation and plastic protective cover. 

Then, press the button and you will hear a clicking noise, which indicates you reset the unit successfully. 

5. Replace the elements to bring the unit into working status. I already mentioned the way of replacing the heating element earlier in this guide. 

6. Raise the temperature by adjusting the thermostat dials. In this case, remove the upper access panel and set the thermostat dials to a higher position. 

7. Verify all the faucets are closed. 

8. Call your local electric utility company. 

9. Let the water heater recover from an abnormal demand by leaving it for several minutes.

10. The cold inlet water takes longer to warm and it’s normal. 

6. Water Too Hot

The water heater will warm the water excessively if you set the thermostat too high or don’t install either covers or insulations. 

How To Fix: 

Set the thermostat too low by accessing the upper thermostat. If you don’t install covers or insulations, reinstall them. 


Thousands of users rely on the Rheem Marathon Water Heater for its reliability and durability. But like other appliances, you may go through some issues with the water heater. 

You can easily resolve those issues by understanding the common problems and their solutions. And this guide is exactly what you are looking for. So, go along with every troubleshooting step I mentioned above. 

Keep in mind; that not every problem can be solved at home. You must seek help from professionals as they have the expertise to fix it. So, don’t hesitate to call a certified plumber. 


  • Rheem Water Heater Reset Button

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