Within two years of purchase, the water heater has lost flame three times. The first occasion was resolved by the manufacturer sending a control module and thermocouple (TC). The second occasion was resolved by the manufacturer sending just a TC. The third occasion was reolved by removing the TC, sanding to bare metal all the way around with 220 sand paper, and reinstalling. I believe a soot covered TC was the problem on all occasions. The TC senses flame, not heat, so cleanliness is imperative. Will try to keep utility room cleaner to see if that helps. Hope this helps someone else.