i bought mod#he40m01aag electric hot water heater about 10 years ago. It has started beeping- kinda like a smoke detector. it woke me up at 3 this morning and wouldn't stop beeping until i ran some hot water in a bathroom sink. It is still beeping- but not constantly. I even turned the power off the the unit and it still beeped. Why is it beeping and what do i do to make it stop.