EPANET - Hydraulic Analysis - Head Loss Formulas

Head Loss Formulas

Epanet hydraulic analysis options offer three different formulas for calculating head loss in a pipe as a function of flow rate.

• Hazen-Williams Formula
  HL = 4.727 * L * Q ^ 1.852 / ( C ^ 1.852 * d ^ 4.871)
  Where:
  HL = head loss (feet)
  Q = flow in (cubic feet per second)
  L = pipe length (feet)
  d = pipe diameter (feet)
  C = roughness coefficient (Hazen-Williams C Factor)
• Darcy-Weisbach Formula
  HL = f * L * v ^ 2 / ( d * 2 * g )
  Where:
  HL = head loss (length)
  g = Gravity Acceleration (Length / Time / Time)
  L = pipe length (length)
  d = pipe diameter (length)
  v = flow velocity (length / time)
  f = friction factor (unitless)
  The friction factor is a function of (e/d) and the Reynolds number, where e is a roughness coefficient with units of length. The above formula can be used with any consistent set of units.
• Chezy-Manning Formula
  HL = 4.66 * n ^ 2 * L * Q ^ 2 / d ^ 5.33
  Where:
  HL = head loss (feet)
  Q = flow (cubic feet per second)
  L = pipe length (feet)
  d = pipe diameter (feet)
  n = roughness (Manning coefficient)