I have a Sears electric hot water heater that just guessing is about 50 gallons. The thing has gotten to when I take a shower the water will be very hot at first but after about 3 minutes the water starts getting cold. It used to have plenty of hot water. It has 2 heating elements. One close to the top and one close to the bottom. I am thinking one of the elements needs replaced. If it stays on for a couple of days it will unset the reset button. Any input is appreciated.