A.O. Smith GCR-40 ProMax Plus High Efficiency Gas Water Heater, 40 gal Blue Diamond glass coating provides superior corrosion resistance to industry-standard glass lining Self-powered electronic gas valve uses thermopile to generate power needed to operate the electronic gas control without requiring external power Internal microprocessor provides enhanced operating parameters and tighter differentials for precise sensing and faster heating response Dynaclean diffuser dip tube helps reduce lime and sediment buildup, maximizes hot water output; made from long-lasting PEX cross-linked polymer Meets all current regulations set forth by the National Appliance Energy Conservation Act (NAECA)