Here is mine. I did not mean the sump overflow I meant the overflow in your display. It depends what kind of overflow you are using if it will work or not but if my return pump were to fail my overflow will not drain below the acceptable water line on my heater. If the power goes out your heater wouldn't run anyways but if your return pump fails you must make sure you know how far down your overflow will drain. Just test it and make sure the heater is below the final water line when the return pump is off. Just an idea