The heart of the cleaning machine is the high-pressure pump, which is in an irreplaceable position. Piston pumps are the most common. Because they are more efficient and have a longer life, the pistons are usually made of ceramics and are very resistant to wear. Piston pumps are often described as a The root piston moves back and forth. Through a fixed seal; while plunger pump seals are mounted on the plunger, through a smooth cylinder wall, plunger pumps generally have better initial service characteristics, but cannot operate at excessive pressure and have a shorter life .

The capacity of the pump depends on the speed of the pump, which must get the same amount of water in and out. Unlike centrifugal pumps, the flow can be increased or decreased. The piston pump has a very stable water flow parameter. No matter how high the pressure is, the flow rate will remain unchanged. The blockage of the nozzle water outlet will cause the high pressure pump to bear too much pressure. Therefore, devices such as pressure relief valves are installed in the system.

 When the piston moves backward, water is drawn into the seal chamber through the inlet valve, and when the piston moves forward, water is forced through the outlet valve to the outlet of the pump. Most piston pumps are double or triple. Dual piston pumps place higher and stricter demands on system components and operators. Triple pumps are the most versatile form of pressure washer due to their ability to produce a smoother flow of water. High-speed pumps produce less pressure loss and require less starting torque. However, it causes faster wear, less suction, and is sometimes louder and potentially damaged.

90% of the failures of high-pressure cleaners are usually not due to the pump. The most common failure is due to the wear of components or parts (such as nozzle seals, etc.). Insufficient water intake in the pump is the primary cause of early failure of the pump. The fit does not allow enough water to enter the pump to cause cavitation. Cavitation causes a small explosion of the gas mixed in the water to cause overpressure damage and wear on the piston surface.