Why should we consider the installation height of the water pump? Under what circumstances must the pump be installed below the water surface of the suction tank?

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If the minimum pressure inside the water pump is lower than the vaporization pressure of the liquid being pumped at its operating temperature, cavitation will occur, causing damage to the water pump. The height at which the water pump is installed above the water surface has a direct impact on the pressure inside the pump. To avoid cavitation, it is necessary to take into account the installation height of the pump, ensuring that the pressure at the lowest point inside the pump is higher than the saturated vapor pressure corresponding to the operating temperature, with a certain margin added for safety. For some axial flow pumps, or in piping systems that transport liquids at higher temperatures (such as heating systems, boiler feed water systems, and steam system condensate systems), the vapor pressure of the liquid at those temperatures is relatively high ； Or the pressure on the surface of the suction tank is lower than atmospheric pressure, creating a certain degree of vacuum; in such cases, the impeller of the water pump usually needs to be installed below the surface of the suction tank.