IP system :
For designing water supply pipeline, which are flowing full under hydraulic pressure.
Where P = the pressure loss in psi per foot of pipe.
Q = flow in gpm (1 gallon= 1 USgallon =3.785 litres).
C = coefficient depending upon roughness of pipe (80 to 140).
d = diameter in inches
SI system :
Pm= pressure loss in bars per meter of pipe.
Qm = flow in litres/min.
dm = diameter in mm.
C = coefficient depending upon roughness of pipe (typically 80 to 140)