Well just look at it carefully and if you hear a noise like air bubbles (or like your bubble strip is out of the water making that hissing noise). TAKE THE HEATER OUT RIGHT AWAY CAUSE THAT'S THE PROBLEM. That is exactly what mine did and i started to see the little white line of crap coming out of the crack in the seaming of the heater. So i ripped it out of the tank and i saw some more white stuff slowing dissipating but coming out. I do have one question What is the white stuff coming out of the heater? if anyone knows?