Here is a good tip from Daly Industrial Supply - When choosing a water pump, make sure that the pump meets the requirement of flow rate and pump lift and complies with economic, safe and applicable principles according to the usage of the water pump.
1. Choosing the water pump according to the usage
Clean water pump: It is used to convey clean water and other liquids whose physico chemical properties are similar to water, and it is applicable to cold and hot water circulation pressurization such as industrial and urban water supply and drainage, pressurized water supply in high-rise constructions, garden irrigation, heating & ventilating refrigeration cycle, farm irrigation, as well as used to match other equipments.
Sewage pump: it is applicable to convey sewage and waste water which contains fibrous dirt, silt and solid particles of certain particle size.
Chemical pump: it is mainly used to transfer and circulate chemical corrosive liquid, and it is applicable to industry, research institute and lab and so on.
2. Water pump that meets the requirement of pump lift
The energy that liquid of unit weight gets from the pump is called pump lift.
The pump lift includes suction, and is approximate to the pressure difference between pump outlet and inlet. It is expressed as H and its unit is meter.
The pump lift of a centrifugal pump takes the impeller central line as measurement datum, and it is composed of two parts. The vertical height from the impeller central line to the surface of water source, i.e. the water suction height of the water pump, is called suction lift and it is called suction for short. The vertical height from the impeller central line to the surface of water tank, i.e. the height of water that water pump discharge, is called discharge lift, and it is called discharge for short.
Water pump lift= suction lift+ discharge lift.
Please be noted that the pump lift indicated in technical parameters refers to the pump lift that the water pump can produce, and it does not include the lift loss caused by the friction to the water flow in the pipeline. When choosing the water pump, please be noted that lift loss cannot be ignored.
The water pump lift is about 1.15~1.20 times of the water lifting height. For an instance, if the vertical height from the water source to water tank is 20 meters, the lift of the water pump needed is about 23~24 meters. The lift indicated in technical parameters of the water pump shall be close to the pump lift needed. In this case, the efficiency of the water pump can be higher and it will be more economical. However, it does not mean exactly the same, and generally speaking, the water pump can also work more efficiently when the deviation is no more than 20%.
Is it right to buy the water pump with pump lift as high as possible?
Of course not..... If the water pump with high pump lift is used in low lift, water flow will be excessive and engine will overload. In long-term operation, the engine temperature will rise and will cause rapid wear of engine parts.