Commonly used materials for electric water heater heating pipes, is: Incoloy 800. Incoloy 840. Stainless steel 316L. copper. Incoloy 800 is currently one of the best outer tube material used in China, basically only used in high-end models. Incoloy 840 is more commonly used. 316L and copper are not very commonly used, but they have advantages in certain water quality areas. Such as certain regions of China (Henan, Xinjiang) and the Middle East. There are more chloride ions (up to 80mg / L) and sulfate ions (up to 140mg / L) in the groundwater. If the groundwater is used directly in the water heater without treatment. The outer tube of the electric heating tube, such as Incoloy 800 or 840, may produce pitting corrosion within a few months (or even within a few weeks) and cause the outer tube of the electric heating tube to be perforated and damaged. But if the tube is 31 6L or copper tube, its service life can reach more than 1-2 years.