Rheem Tankless Water Heater E5 Code

Rheem Tankless Water Heater E5 Code (Too Much Water Flow)

Rheem Tankless Water Heater E5 Code indicates the water flow is too much, and the unit can’t keep up with the demand. As a result, your tankless water heater fails to produce enough hot water and throws the fault code E5. 

Limiting the water flow, you can clear the error code E5. You can install a flow regulator to restrict water flow to a specified flow rate. 

Below, I will show you how to install the flow limiter to regulate the water flow to a specified flow rate. So, let’s dive in. 

How To Fix Rheem Tankless Water Heater E5 Code?

Excessive water flow is the main culprit behind the error code E5. To ensure optimal temperature output and overall performance of the unit, you should install a flow regulator. 

It will help you limit the maximum volume coming out of the unit to a specified flow rate to prevent the exit temperature from becoming too cool. 

Now, it’s time to go along with the followings steps to choose and install the flow regulator, which will help you erase the error code E5: 

  • Find your water heater input in the chart on the left.
  • Select the column with the inlet water temperature closest to your geographical location. 
  • Take the GPM you find and match it with the corresponding flow regulator on the right.

Once you choose the correct flow regulator, move forward to install it. You can check out this link to get the flow regulator. 

1. Turn off the power to your tankless water heater at the circuit breaker.

2. Turn the water supply off to the water heater by closing the hot and cold water supply valves. 

3. Disconnect the hot outlet as we should install the flow restrictor there. Don’t forget to drain some water before unscrewing the hot outlet connection. Regarding this, open some hot water fixtures and drain the unit. 

Removed the hot outlet connection and catching the water drippings

4. Once you drain the water, use an adjustable wrench to remove the hot outlet connection. Put a pot under the hot outlet to catch the drippings. 

5. Choose the right size flow restrictor insert following the guidelines above and snap it into the connection as you can see in this picture: 

Put a flow restrictor insert inside the flow regulator

Then, place the rubber washer inside the flow restrictor. Next, install the flow restrictor at the hot outlet and complete the installation by connecting the hot water hose. 

Installed the flow regulator

Lastly, turn on the cold water supply valve to let the water go through the unit. Then, restore the power to the unit and turn on the unit by pressing the power button. I hope it will reset the error code E5. 


Error code E5 On Rheem Tankless Water Heater means that for the given input temperature, the water heater fails to keep up with the flow of water coming through your system. This could mean you end up with a bathtub full of lukewarm water.

And the flow regulator will cap how much water can flow through your water heater. It means you can’t  fill your bathtub as quickly but it will avoid the lukewarm water situation. 

Fortunately, I described how to choose and install the flow regulator. So, follow the guidelines and have the error code E5 reset. 


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