Enter the hydraulic mean radius, dimensionless constant of particles, the specific gravity of the solids, manning’s roughness coefficient, and the diameter of the solids into the calculator to determine the self cleansing velocity.

Self Cleansing Velocity Formula

The following equation is used to calculate the Self Cleansing Velocity.

Vs = 1/n * R ^(1/6) * SQRT ( B*(Gs-1) * ds )

  • Where Vs is the self cleansing velocity
  • R is the hydraulic radius
  • n is the Manning’s coefficient of roughness
  • B is the dimensionless constant of the characteristics of the particles
  • Gs is the specific gravity of the particles
  • ds is the diameter of the particles.

What is a Self Cleansing Velocity?


A self cleansing velocity is the minimum velocity of flow required to prevent particle build up.

How to Calculate Self Cleansing Velocity?

Example Problem:

The following example outlines the steps and information needed to calculate

First, determine the variables in the equation above:

R = 2

n = .25

B = .45

Gs = 1.25

ds = .45

Finally, using the formula above, calculate the self cleaning velocity:

Vs = 1/n * R ^(1/6) * SQRT ( B*(Gs-1) * ds )

Vs = 1/.25 * 2 ^(1/6) * SQRT ( .45*(1.25-1) * .45 )

Vs = 1.0102