No, not water heater stuff. It was just the way they made these kzs, i think it only lasted 2 years because there a pita. One is for the siphon, the others change the direction of the water from the pump to the tank. So , sort of like diverter valves. Screw one up and because im an idot and never mark them, you spend an hour turning them back and forth and still dont know if you have it set corectly to fill the tank. And as i said ,under the couch and slide, so if its wrong no water in the tank. So the valves are un marked and on the water lines in and around the pump. They are not for the water heater, those are seprate.
Now that you mentioned the overflow, i will see if it needs to be blown out, that could also be why it takes a while to fill. Not sure because i might have the valves in the wrong spots!