fox@srfox.net
Senior Member
That is your hot water tank bypass valve. Close the other two valves and you will not have hot water but both taps will be cold water.
Justin, you're in luck. Not only will your water heater have one, but it will have two; one for 12V and one for 120V. They are located under the black rubber-covered reset buttons. When you remove one, look for the code (part) number printed on it and then run it down on Google. That way you will be able to tell if you want one warmer or cooler. I might also add, twenty minutes and two gallons of cheap antifreeze will give you a world of peace all winter long.