Equivalent pipe is defined as the pipe of uniform diameter having loss of head and discharge equal to the loss of head and discharge of a compound pipe consisting of several pipes of different lengths and diameters. The uniform diameter of the equivalent pipe is called equivalent size of the pipe.
Le
De5
=
L1
D15
+
L2
D25
+
L3
D35
+−−− This equation is also known as Dupuit’s Equation.