Relatively speaking, thick tubes have a large heat collection area, fast heat collection, and high water temperature. Therefore, solar water heaters using thick tubes should be given priority when purchasing. There are mainly two types of materials for manufacturing vacuum tubes: single-target machines and three-target machines. Among them, the quality of three-target machines is better, and consumers can identify them by their appearance when purchasing. The vacuum tube of the single-target machine is gray in color, with color difference, and the inner wall of the vacuum tube is light black; while the vacuum tube of the three-target machine has a bluish appearance, no color difference, and the inner wall is dark red. Second, weigh the weight: The water tank is very important for the water heater. Generally, water tanks with heavy weight are of good quality. The weight is mainly determined by the material of the water tank shell and the foam layer between the water tank shell and the water tank liner. Generally, the shell of a poor water tank is made of shiny stainless steel (currently many big cities have banned the use of water heaters made of this material due to the presence of light pollution), and the shell is not thick enough and lightweight. The foam layer is directly related to the insulation effect of the water heater, so it is also very critical for the use of the water heater. Generally, the foam layer of famous brand products is foamed by machine at high pressure, so that there is no air between the outer shell and the inner tank, and the foam layer is dense and thick. Therefore, the entire water tank is often heavy to weigh. Three comments on the bracket: In general, the brackets of solar water heaters with good quality are made of color steel plates or aluminum alloy brackets with a thickness of 1.5mm. They are fine in workmanship, have reasonable mechanical angles, are thick, strong and durable.