The ECO stands for Energy Cut-Off, and is installed in both gas and electric water heaters. Here is how General Electric describes it in their owner’s manuals for electric water heaters: “The water heater is equipped with a combination thermostat and high limit Energy Cut-Off control (ECO) that is located above the heating element in contact with the tank surface. If for any reason the water temperature becomes excessively high, the high limit control (ECO) breaks the power circuit to the heating element. Once the control opens, it must be reset manually."

    The ECO safety device is intended to keep the water heater from overheating the water to the point that it boils and the tank explodes. ECO acts in tandem with the Temperature-and-Pressure-Release (TPR) valve on the side or top outside surface of the water heater, which opens to release the super-hot water if the tank actually does overheat. 

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Here’s links to a collection of more blog posts about WATER HEATERS:

• Can a Temperature and Pressure Relief (TPR or T&P) valve be mounted to discharge horizontally? 

• Can the temperature and pressure relief (TPR) valve discharge pipe for a mobile/manufactured home water heater terminate under the home? 

• What are the most common installation mistakes with water heater replacement?

• Where are gas water heaters not allowed to be installed?  

• What does it mean when a water heater Temperature/Pressure Relief (TPR) discharge pipe is "trapped"? 

• Does a water heater need a shut-off valve? 

• Does a tankless gas water heater still work with no electricity during a power outage?  

•  Why do water heaters have a sacrificial anode? 

• When is a water heater drain pan required?

• Why is there water in my water heater drain pan?

 • Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises? 

• What can I do to make my water heater last longer?

• What's that powdery crust on the pipe connections at the water heater? 

   Visit our WATER HEATERS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.