Hotsy direct-drive pump for pressure washers

Direct Drive Pumps

A "Direct Drive" pump has a hollow shaft, which simply slides onto the drive shaft of a motor or engine. The flange on the pump is mounted to the face of the engine or shaft end of the motor. Normal gasoline engine speed is about 3450 RPM. Since the pump is connected directly to the engine shaft, the pump RPM is the same as the engine RPM. Electric motors typically will turn a direct drive pump at 3450 RPM or 1725 RPM. Direct drive pumps allow for a more compact designed pressure washer. Another advantage is that this drive system is simple, with fewer moving parts; therefore less expensive. The disadvantage is by having the pump spin as much as the engine or motor, the bearings and other parts get more wear and tear, reducing the life span of the pump. Direct drive pressure washers transfer the vibration of the engine or motor directly to the pump. Also, the faster pumps of direct drive pressure washers are spinning so fast that they cannot draw water from a tank very well. However, they tend to work just fine when the water is forced into the pump, like when it is hooked-up to a hose.


Benefits of Direct Drive:

  • Compact Design
  • Lower Acquisition Cost

Disadvantages of Direct Drive:

  • Reduced Life Span
  • Cannot Draw Water from Tank or Standing Water Source


Hotsy belt-drive pump for pressure washers

Belt Drive Pumps

A "Belt Drive" pump has a pulley mounted to its solid shaft and is driven by one or more belts that are attached to a pulley on the motor or engine. The pulley system allows these pumps to turn at a much lower RPM than a direct drive pump (typically 900-1400 RPM). The belt drive pump crankcase has a larger oil capacity. This, combined with the lower RPM of the belt drive pump, allows the pump to run much cooler than a direct drive pump. The pump is isolated from the heat of the engine or motor, also. Belts and pulleys also absorb vibration, reducing pump fatigue. Because of these factors, most heavy use pressure washer applications will demand a belt drive pump. The disadvantage of this system is there is some loss of efficiency due to the additional friction from the belts and pulleys. Plus maintenance is required occasionally to adjust the belts. However, all other things being equal, the belt drive system should provide for the longest pump life.


Benefits of Belt Drive:

  • Vibration Absorption
  • Lower RPM
  • Lower Operating Temperature
  • Longer Life

Disadvantages of Belt Drive:

  • Loss of Efficiency
  • More Maintenance Required