Reasons for the decrease in efficiency1. Due to the scouring of the water flow, the inner wall of the pump flow channel and the impeller through the water surface become rough and uneven, the friction coefficient of the flow channel in the pump increases, coupled with the large flow rate of water in the pump, the head loss increases. Reduced hydraulic efficiency.2. Due to the addition of drugs or water quality before the pump, serious fouling or corrosion in the pump casing. Serious fouling in the pump casing can increase the wall thickness of the pump casing by about 2ram, and the inner wall of the pump forms a scale tumor, which reduces the volume of the pump body, reduces the amount of pumped water, and the flow channel is rough, and the head loss increases. Both passenger capacity and hydraulic efficiency are reduced.3. Due to casting defects, cavitation, abrasion, corrosion and chemical erosion caused by the water pump processing technology, cavities or cracks are generated in the pump flow channel, and energy loss is caused by vortex when the water flows. Reduced hydraulic efficiency.4. Cavitation on the surface of the impeller. Due to the negative pressure generated when the blade back water surface is running, when the pressure Pk < Pva, the steam cavity and honeycomb surface are generated, and the pump blade is cavitated under the action of electrochemical corrosion.5. Volume loss and mechanical loss. Due to the long service life of the pump, mechanical wear causes leakage and increased resistance, which reduces volumetric efficiency and mechanical efficiency.The above reasons make the performance of the pump worse. The operating efficiency is reduced by 2~5%, and the efficiency of the pump can be reduced by more than 10%.