Friction Loss in Pressure Washing

Kris Meyer

Friction Loss is a Critical Consideration in Pressure Washing that
Affects Overall Performance & Efficiency

By understanding and managing friction loss effectively,
operators can optimize their equipment,
enhance cleaning outcomes, & improve operational efficiency.

What is Friction Loss?​

Friction loss refers to the pressure drop that occurs as water moves through hoses, pipes, fittings, and nozzles due to friction against the surfaces of these components. This loss reduces the pressure at the nozzle compared to the pressure at the pump outlet.

Factors Affecting Friction Loss​

  1. Hose Length and Diameter: Longer hoses and smaller diameters increase friction loss because they provide more surface area for friction to act upon.
  2. Smoothness of Interior Surfaces: Rough or corroded hoses and pipes increase friction loss compared to smooth surfaces.
  3. Water Velocity: Higher water velocities result in greater friction loss. This is why using the right nozzle size and pump pressure is crucial.

Calculating Friction Loss​

Friction loss can be calculated using formulas that take into account factors like hose length, diameter, flow rate, and type of material. The most common formula used is the Darcy-Weisbach Equation ΔP = f⋅DL⋅2gv2


  • ΔP = Pressure loss (friction loss)
  • f = Friction factor (depends on the material and surface roughness)
  • L = Length of hose or pipe
  • D = Diameter of hose or pipe
  • v = Velocity of water flow
  • g = Acceleration due to gravity

Practical Implications​

  • Optimizing Equipment Selection: Choosing hoses, pipes, and nozzles that minimize friction loss for maximum cleaning efficiency.
  • Maintaining Pump Performance: Ensuring the pump can maintain adequate pressure at the nozzle for effective cleaning.
  • Calculating Required Pump Power: Determining the necessary pump power to overcome friction loss and achieve desired cleaning results.

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