If the water continued to run after all or even most of the hot water was out of the tank, then the valve is defective. The heater could also have a problem which caused the valve failure, but it is not necessarily so. Replace the valve and then test the water heater elements and thermostats.: My hot water heater popped the overheat release valve during the middle of the night, and drained all the water in the tank through my outside outlet (THANK GOD!). I have a well, and it also continued to draw water from my holding tank to fill up the tank. At this point, is it the element that would just need to be replaced? And do I need to replace the overheat valve that popped, or does it just go back? Any help would be appreciated! Thanks, Brian