Pipe Headloss : Modified Hazen-William

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Hydraulic Gradient Calculator for pressure flow in Circular Conduits

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Formula

The Modified Hazen Williams formula is derived from Darcy Weisbach formula and is as below;

V=3.83*Cr*d^0.6575*(gs)^0.5525/nu^0.105

Where,

V = Velocity of flow,

Cr = Coefficient of Roughness,

d = Pipe Diameter/sec,

g = Acceleration due to gravity,

s = Hydraulic Gradient,

v = Viscosity of Fluid

For circular conduits, headloss in circular conduits is given by

h=L*(Q/Cr)^1.81/994.62*D^4.81

Where,

Q = Flow in Cum/sec,

L = Length of Pipe in meters,

D = Internal pipe Diameter in meters,

Cr = Coefficient of Roughness,

h = headloss in meters,

Coefficients

The coefficient used for different pipe material are as follows;
Pipe Material
Diameter (mm)
 
Velocity (m/sl)
 
CR Value when new
CR Value for design period of 30 years
FromToFromTo
RCC10020000.31.811
AC1006000.3611
HDPE/PVC201000.31.811
Cl (for water with positive Langelier's index)10010000.31.810.85*
Cl (for waters with negative Langelier's index)10010000.31.810.53*
Steel (for waters with negative Langelier's index)10020000.32.110.73*
SGSW1006000.32.111
Gl (for waters with positive Langelier's index)151000.31.50.87*0.74