Eternal Tankless Water Heater Troubleshooting (Complete Guide)

Grand Hall, the producer of the Eternal tankless water heater, packed up operations in North America. Their departure has left millions of users of these units with problems that the company cannot repair for them.

Several common issues faced by owners of this water heater include:

  • Mixing control valve initialization failure
  • Abnormal noises coming from the unit
  • Low-temperature water outflow
  • A burner that won’t ignite

Are you thinking of replacing the unit with brands like Rheems? Hold on, as many of these problems are fixable by using replacement parts from other brands.

This article will explore the more frequent issues owners of this heater face and outline DIY solutions.

eternal tankless water heater

Common Problems with Eternal Tankless Hot Water Heaters

The Eternal tankless or hybrid water heater provides almost instantaneous heat. It has a heat exchanger with a large surface area that utilizes 145,000 BTUs to deliver continuous hot water. 

And with an operating cost of less than $115 per year, the Eternal tankless heater is in a class of its own.

However—as you have discovered—it is not all sugar and spice with the unit. This hot water heater may develop one or more of these problems within a few years of use:

Cannot Regulate Temperature

Is the water not hot enough or too hot? If your unit can’t maintain the right temperature, it’s time to examine these components:

  • The temperature setting
  • The cold water supply line
  • The gas supply line

To troubleshoot, start by checking if the temperature setting is correct. 

Next, examine if debris or sediments are clogging up the cold water supply line. Some cities’ water supplies contain mineral deposits that may accumulate within the supply line and restrict water inflow. 

Eternal tankless water heaters may also run on natural gas or liquefied gas. If yours runs on gas, it won’t function with an incorrect gas supply line. 

Check the gas meter rating at the front of the unit to know the correct gas type for the unit. Also, ensure the gas supply pressure is within the proper range:

  • 3.5 to 10.5″ WC for Natural gas
  • 8.0 to 14″ WC for Propane or LG.

Loud Backfiring

This issue is quite common in Eternal GU195 models. Sometimes, you may hear the loud backfire every ten seconds. 

Tankless water heaters will make loud backfire noises when there’s a leak between the exhaust and the sealed chamber, there’s low gas pressure, or the venting termination is incorrect. 

Additionally, an incorrect venting termination may trigger abnormal noises or backfiring. For this, you’ll need to call a licensed repairer to fix the vent termination.

To fix the noise, check if the gas valve is fully open by examining it for blockages. Liquefied or natural gas gives off the smell of rotten eggs, which should hint you off to any gas leaks.

Still not sure? Pour a mixture of water and soap on the suspected area and wait to see if it bubbles. These bubbles indicate a gas leak. 

Burner Won’t Light

There are a few possibilities for a burner that won’t ignite.

First, the cold water supply line could be too close to the gas supply line. Second, your unit might not be switched on. You could also have a faulty pilot light.

Check the power outlet and the 3A fuse to verify that the unit is receiving power. Plug in or switch on the unit if the display screen is blank. 

If the unit is switched on, check the supply lines. Be sure to separate the cold water and gas supply lines. Also, verify that the gas and water valves are unobstructed and fully open and that the water flow rate is above 0.5gpm. 

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How to Troubleshoot Error Codes in Eternal Tankless Water Heater

water heater troubleshooting

Sometimes, error codes suddenly show up on the unit’s screen. Don’t fret—these codes can actually tell you all you need to know about what’s going wrong. Here are some of the most common ones:

E1 Error Code

Eternal tankless heaters will display an E1 code when the pilot light is still on despite switching it off. You should call your local repairer to resolve the issue.

E2 Error Code

The E2 code in Eternal tankless water heaters indicates an ignition failure. To solve this issue, examine these components;

  • The ignition and 8p wire connection
  • The gas valve and pressure
  • The gas line, flame rod, and ignitor

E3 Error Code

Is your unit displaying an E3 code? Then, the problem is abnormal combustion. So, check the gas line for defects, and examine the gas supply. Also, examine the voltage supply to ensure it meets the requirement.

E4 and E5 Error Codes

The E4 and E5 codes reveal a faulty thermistor. This small device turns your hot water heater on or off in response to the water temperature and will shut off the unit once it exceeds 140°F. 

Use an ohmmeter to test the thermistor. A faulty thermistor will give a reading far from its rated value. Also be sure to check the connection between the thermistor and the 14p wire. 

E6 and E9 Error Codes

The E6 and E9 code also indicates a faulty thermistor. Here, the H/E thermistor is the culprit. Use an ohmmeter to check the rated value. Consider calling a licensed technician to replace it.

E27 Error Code

The Eternal tankless hot water heater will display the E27 code if there’s a problem with the mixing control valve. You will need to replace the faulty valve with a new one. 

Here’s the problem: There are no replacements for faulty mixing control valves. To solve this dilemma, use the mixing valve from the Rheem #RTG20298N.


Don’t give up on your Eternal water heater just yet! Follow this troubleshooting guide to solve common problems in this unit using essential electric tools and parts from other brands. If needed, hire a licensed technician to handle more complex repairs.