Skip to main content
All CollectionsCommunity-DIY-ReviewsTroubleshooting Help
Steps on how to check and resolve an E0 error code in an Eccotemp 6.5 GPM Builder Series Tankless Water Heater
Steps on how to check and resolve an E0 error code in an Eccotemp 6.5 GPM Builder Series Tankless Water Heater
Updated over a week ago

Eccotemp received an email from a customer saying they are experiencing an E0 error code in their 6.5 GPM Builder series Tankless water heater. The customer has provided pictures of their water heater below.

Rights and Wrongs of the Installation

The image above illustrates an improper installation of the 6.5 GPM Builder series Tankless water heater. The Red Arrow (1) points to the vents as the customer mentioned. They used galvanized materials, not category II or III stainless steel venting.

Regarding the water connections, the White Arrow (1) indicates the use of appropriately sized 3/4" water pipes.

As shown by the White Arrow (2), a 3/4" flex line connection is correctly employed for the gas connection as well.

Also, we have let the customer know to make sure that gas pressure falls within the acceptable range, specifically between the minimum and maximum inches of water column.


The E0 error code on a 6.5 GPM Builder series Tankless water heater pertains to the outgoing and incoming water temperature sensors.

  • First, we advised the customer to check and reset the inlet and outlet temperature sensor that is found in the water heater’s computer board.

  • Second, we advised the customer to check if they were currently having inconsistencies in their power supply as it might be a cause of concern for the internal wires to be damaged over time.

  • Third, we recommended to use of a stainless-steel material of Category III for venting, required by CSA for safety standards. If a customer uses other incompatible material for venting it can cause too much acidity in the exhaust and cause damage to the internals of the water heater. The stainless steel handles the exhaust temperatures safer and more efficiently.

How we fixed the E0 error code for the 6.5 GPM Builder series Tankless water heater

After confirming that the vent pipe connected to the water heater had a blockage due to the winter season and was about 12 feet long, we advised the customer to clear the blockages, change their venting setup, and consult a professional plumber to install the right venting setup.

We also advised the customer that if their setup has been changed into the standard installation, they could check and do the following steps in reseating the wired connection inside the water heater.

The outlet temperature sensor is located on the outgoing water pipe, which is located inside your 45 model, in the bottom left corner behind the computer board.

  • Step 1:

To access the sensor, unplug the water heater from the electrical outlet, turn your gas source off to the heater, and remove the cover by unscrewing the four screws that hold it in place.

  • Step 2:

After doing so, remove the computer board by removing the two screws located at the bottom corners of the gray plastic saddle that houses the computer board.

  • Step 3:

Once you have located the outlet temp sensor (which is a white cord, with a brass nut that connects to the bottom of the copper pipe), then find trace the outlet temp sensor's connection to the computer board, unplug the connector, and reconnect it.

The connector goes to the top right corner of the computer board. That goes the same with the inlet water temperature sensor. That is the white plastic in front of the flow meter sensor. Please see the photos below for your reference.


Following the customer's completion of the troubleshooting steps outlined above, the 6.5 GPM Builder series Tankless water heater operated seamlessly, and the E0 error code was successfully resolved.

The issue stemmed from a galvanized vent and a restricted vent pipe. We have further reiterated the importance of changing and clearing the vents to the required vent kits for the water heater.

We always recommend taking advantage of our Free Pre/Post Purchase Consultation call with one of our experts to better understand the uses, installation, and common mistakes made when installing one of our products.

We also always recommend hiring a professional licensed installer to ensure your installation is correct and intended for the product you purchased.

Here at Eccotemp, we understand the importance of a successful installation, which is why we provide pre-sale and post-sale product consultations. Our team can offer guidance on essential aspects of tankless water heater installation, including sizing, venting, and safety considerations. We’re here to support you throughout the entire process.

To take advantage of our consultation services or to schedule a call with one of our experts, please visit our booking page. Investing in professional installation and seeking expert advice ensures that you get the most out of your tankless water heater and enjoy reliable, energy-efficient hot water for years to come.

Click here to schedule your call with our team today!

Did this answer your question?