Storage water heaters 30% to 50%. China has a vast geographical area and has complex water quality. Some regions directly use groundwater sources that have not been treated too much. The calcium ions and magnesium ions in the water are relatively large, and it is easy to foul the surface of the stainless steel heating body and make the heat transfer performance of the heating body worse. Tube surface temperature is high. At the same time, this kind of fouling is loosely shaped. The performance of the electric heating tube is still in contact with water, but the heat transfer is relatively poor. The upper surface of the outer tube and the inner surface of the fouling will generate vaporization and form cavitation. That is, when heated, water will form water vapor and then become a bubble. When the bubble reaches a certain level, it will be broken and a vacuum will be generated at the moment of rupture. The surface of the heating tube has a positive pressure when bubbles are generated. When the bubbles are broken, negative pressure is generated. The surface of the heating tube is continuously affected by the change of the stress, and a cavitation phenomenon occurs slowly, resulting in damage to the stainless steel electric heating body. In addition, if the water contains too much chloride and sulfate ions will also pitting the surface of the stainless steel heating pipe, for example, in China's Central Plains and Xinjiang region is the use of groundwater, chloride ions and acid ions are more, these areas due to points Corrosion causes perforation of the stainless steel heating body, causing water to enter the interior of the heating pipe, causing leakage, poor insulation, causing failure of the protection function inside the machine and requiring maintenance. It can be said that the instant electric water heater stainless steel heating element more than 60% is due to scaling or pitting damage. If the company's market sales can reach a certain scale, then different heating pipes can be selected according to the water quality of different regions. For example, the use of 800 stainless steel heating pipes placed in these areas of poor water quality, can reduce the product repair rate, while enabling the performance of the product to be improved, and mass production will not increase the cost much. However, if the sales cannot reach a certain scale, the cost of using 800 stainless steel pipes will be very high.