Why My Rheem Water Heater Beeping [Reasons + Solutions]

Rheem water heater beeping is an alert from the heater, indicating some malfunctions going through the water heater. 

The root reasons behind this system alert are buildup limes scale, water leakage, overheating warning, high water pressure, and faulty thermostat. Poor water flow, blocked air inlet, and overloaded system are some culprits that can make a water heater beep.

rheem water heater beeping

Most often, the water heater starts beeping when it detects some errors in the system. While showing error messages 11, 12, & 13, the heater will make a beep and go to shut-off mode. 

To solve the errors, you need to address the code and detect the related issues. Throughout this article, we have explored each of the aspects relating to heater beeping with quick-solving methods.

Why Is My Rheem Water Heater Beeping [Reasons + Solutions]

Here are the reasons that are responsible for making a beeping noise in your Rheem water heater are described in detail. Also, you will know how to break down each of those issues more effectively.

Note: You can also read how to fix Rheem Water heater 6 3 flashes.

1. Build-Up Of Limescale

The water that passes through the tankless water heater contains various minerals, including calcium and magnesium. When the water runs in the heater, the heater’s metal components, such as heat transfer, absorb the minerals.

These mineral particles stuck up in the heater and degrade water heater efficiency and reduce the heater’s effectiveness. From the limescale buildup, you will hear a strange popping sound. As this harmful coating is dangerous from a health perspective, so you need to descale it immediately.

How To Descale A Tankless Water Heater

The only solution for descaling the buildup of sediment from the heater metal component is flushing your water heater. Almost all the well-known brand manufacturers recommend flushing the heater at least once a year. 

flushing heater with vinegar through the hose

It will eliminate the buildup of minerals from the heater inside. Flushing hot water with white vinegar is highly popular and effective as well. Either you can flush or descale the limescale by yourself, or you can contact any certified plumber for this. 

2. Water Leakage

Water leakage is another common reason for beeping in the water heater. There has a water leakage sensor in every modern water heater. The leakage issue creates by the defection of this sensor as well. 

When the heater senses a leak, it produces an audible beep as alertness. In many cases, the heater goes to shut-off mode after sensing the leak or defect in the leak sensor.

This happens to prevent leaking water from damaging the unit or your property. However, some of the leading reasons why tankless water heaters leak include:

  • Improper installation of the heater
  • Weak pipe connection
  • Excessive water flows through the system
  • Blockages in the pipes
  • Poor venting system
  • Bad water conditions (hard or acidic water)
  • Building rust inside the system

How To Fix A Leaking Tankless Water Heater

  • If you notice any evidence of leakage, you will have to find the source of the leakage.
  • Check the leak sensor. Verify all the wiring connections are secured and have not any damage.
  • Turn off your heater and disconnect the sensor. 
  • Now turn on the hater. If the heater starts in fine condition, be sure the sensor is the culprit. Replace the defective sensor. 
  • Ensure a proper installation of the venting systems.
  • Clean out the blocked inlet and outlet pipe. 
  • Then, you have to find visible leaking signs on the heat exchanger or pipelines.
  • If there have severe damage, it is a good recommendation to hire a certified plumber to fix these problems. 

3. Overheating

Most often, a beeping sound from the water heater is a warning that the unit is overheated. A faulty heating element or a defective temperature sensor leads to the system overheating. 

Also, there features a sensor named Overheat Film Wrap in the Rheem water heater. It starts beeping when it senses excessive heat from the heat exchanger. For this, the heater will catch the error code 14.

The other leading reasons for heater overheating are clogged exhaust venting, damaged heat exchanger, improper venting system, wrong thermostat setting, and incorrect fuel supply. 


  • First, check the venting system of the heater. Clean the venting pipes and make them clogged-free.
  • Look at the heat exchanger. There should not have any build-up of sediment or corrosion. If needed, replace the faulty heat exchanger.
  • Check the placement of the thermostat. Verify if it is working and set the temperature correctly.
  • If required, consult the plumber to fix the overheating issue more precisely.

4. High Water Pressure

In most cases, the water heater will beep to signal excessive water pressure within the heater system.

 high water pressure

High water pressure is good for a heater, but when it crosses the safe level, it causes a lot of problems in the heater. It damages the heater element and can also cause leaks in your water heater. 

How To Adjust Water Pressure In Tankless Water Heater

Follow the below instructions to measure the water pressure and how to correct it:

  • Take a pressure gauge attached to a hose bib to measure the water pressure.
  • Connect it to an outside hose connection or an inside hose connection to your home water line.
  • The maximum PSI is about 80PSI for your home. Now, if the reading is about 60-65 PSI, it tells high-pressure efficiency in your tankless water heater. 
  • Now, you need to install a whole house reducing valve and set the level there at 60 PSI to maximize the water flow.
  • Also, users need to concentrate on regular maintenance. Remove and clean out the accumulated debris on the faucet aerators and showerhead. 
  • Contact any certified plumber for this purpose.  

5. Faulty Thermostat

In every tankless water, you will find one or two thermostats that are used to control the electrical current flow to different parts of the water heater. This essential device senses the presence of heat.

In the case of the faulty thermostat, the heater fails to ignite and heat the tank water. This situation catches an error in the heater and lets you know about the fault by beeping.

How To Test A Water Heater Thermostat

You need to check for the continuity of the thermostat by following the below steps:

  • First, turn off the power connection from your water heater. 
  • Remove the upper cover of the heater to access the thermostat. 
  • Look for the reset button on the upper thermostat. It will get tripped if the heater gets overheated. Reset the button.
  • Take a multimeter and set the red dialer to the lower setting.
  • Connect one lead off the multimeter to the left side terminal by the reset button. Attach the other lead to the other terminal of the reset button’s left side.
  • If the reading doesn’t close to zero, be sure the thermostat is defective and needs replacement.
  • Repeat the test on the right-side terminals in the same way. Test the lower portion of the thermostat and check for continuity.  
  • Call a certified plumber to replace the faulty thermostat.

6. Poor Water Flow

All the water heaters have a minimum flow rate required to continue the heater operation. The flow of water rate is measured in gallons per minute. 

poor water flow

In the case of the Rheem Gas Tankless Water Heater, the rate should be 0.26 GPM as a minimum water flow rate.

If the flow rate is less than the minimum rate, the heater will shut down and start beeping as an error indication. The leading reasons for low water include:

  • Deposits inside the heat exchanger
  • The shut-off valve
  • Defective flow sensor
  • Blocked inlet filters
  • Sediment build-up in the faucet
  • Blocked and narrow water outlets
  • The wrong installment in cold water and hot water line

How To Increase Water Pressure In Tankless Water Heater

  • Start troubleshooting by inspecting the heat exchanger and cleaning it of any stuck debris.
  • Inspect the inlet filter and the aerators of the faucet. Look for the build-up of silt or grit there. Remove all the obstructions to increase the water flow.
  • Also, build-up limescale in the pipeline also causes the low water flow. Clean it as well.
  • Verify the flow sensor of your Rheem water heater is in good working condition. Replace the damaged one.
  • Now make sure the proper installment of both cold water and hot water lines that should be in sequence.
  • Call a certified plumber for this purpose.

7. Blocked Air Inlet

An air inlet of your water heater supplies air to continue the combustion process. Through the air fan, the fresh air lets in the heater. Besides, the waste gases vent out through the exhaust vent. 

Now, if the air intakes, circulating fans, or exhaust vents are blocked by debris, an error warning will appear as a beep, and the heater will shut down.


  • Check out the air vents and exhaust vents of the heater. You will find dust, dead insects, lint, and bird nests building up there. Clean the vents and make them clogged-free.
  • Besides, the venting materials would be damaged or broken, which you need to replace immediately.

8. System Overloaded

Like another tankless water heater, the Rheem water heater has limitations on the hot water supply every minute. The water heater has a flow rate capacity that tells you how much water will need to supply per minute. 

Now, if the user crosses the limit by opening too many hot water faucets at once, the temperature or the water will drop. That time, the heater will catch an error and start beeping. Besides, the heater will shut down to prevent damage.


  • Once the system is overloaded, you need to reduce the hot water supply by turning off some of the faucets. Then the heater will do a system reset by itself.
  • If not, you have to do a manual reset.  

9. Rheem Tankless Water Heater Beeping 11 [Ignition Failure]

Bepeeing 11 in your Rheem water heater tells you that there is an issue with the water heater’s ignition or ignition failure. The root reasons are:

  • Insufficient fuel supply
  • Restricted gas flow valve
  • Faulty gas solenoid valves
  • Damaged igniter wire harness
  • A dirty burner
  • An electrical outage
  • Insufficient airflow

How To Fix Error Code 11 On Rheem Tankless Water Heater

  • Before moving the detailing, check out the gas tank first and check if there has enough fuel in the tank. If not, refill it.
  • Check the gas valve. Ensure the valve is open and free from dirt or residue buildups. 
  • Don’t miss checking the gas solenoid valves. Here the main burner will not work, but the igniter and the fan function define faulty solenoid valves. Replace the faulty valve
  • Inspect the igniter wiring for damage. Call a professional electrician to replace the defective wiring.
  • If all above fails, replacing the igniter will solve the issue. 

10. Rheem Tankless Water Heater Beeping 12

Beeping 12 on your tankless water heater is the error indication of flame failure. This warning message happens due to the following reasons: 

  • A defective gas control valve
  • Dirty Flame sensor
  • Insufficient gas pressure
  • Gas lines too small for the BTU load
  • Clogged venting
  • Defective heat exchanger
  • Damaged flame rods 

How To Fix Error Code 12 On Rheem Tankless Water Heater

  • First, check out the flame sensor. Cleaning this element will resolve the issue.
  • Then check each heating element, including the flame rod, heat exchanger, and gas control valve. Replace the defective ones.
  • Resolve the gas supply issue by cleaning the kinked hose or by opening the closed gas valve
  • Check the high and low gas pressure of the heater. Contact the plumber for a better understanding. 

11. Rheem Tankless Water Heater Beeping 13 [Activated ODS]

When the ODS is activated, the heater triggers error 13 and indicates with the beep. Here the heater fails to solve the combustion issue of the unit. The responsive factors for this code are:

  • Defective ODS thermocouple
  • Improper manifold gas pressure
  • Defective flame rods
  • Clogged venting system and air intake filter 

How To Fix Error Code 13 On Rheem Tankless Water Heater

  • Clean the dirty flame rods using 100-grit sandpaper.
  • Unclog the air intake and venting system
  • Replace the defective ODS thermocouple.
  • Don’t miss adjusting the burner manifold pressure correctly.


How do I reset my Rheem water heater?

There features a reset button on the heater to perform a reset. Open the panel cover, and you will find a resetting button behind the insulation. Just press and hold the button to reset the heater. 

Why does my tankless water heater need to reset?

The reset button will repeatedly trip when the heater faces several larger issues. Like a faulty thermostat, power outage, grounding problem, a malfunctioning high limit switch, loose wiring connection, or short circuit in the heating element.

To Wrap Up:

Rheem tankless water heater beeping alerts that something is wrong with the heater system. It tells you that some essential heating elements are defective that need your attention. 

So, diagnosing this issue will not be so tough as long as you know the responsive factors for occurring this beeping. Expectantly, our above comprehensive guide has assisted you a lot in finding out the source of the problems and solutions. 

Still, if you have any questions that have been left out, don’t be late to ask us through comments. We’re ready to help you.

About William

William is the founder of Fireplacehubs.com. He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

1 thought on “Why My Rheem Water Heater Beeping [Reasons + Solutions]”

  1. A water heater unit beeping indicates trouble, in our opinion. It’s possible that the system has a leak, that the thermostat or sensor is broken, that the temperature and pressure relief valve is broken, or that the device has obstructions.


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