Manning's Formula for Discharge in CPHEEO Manual on Water Supply and Treatment, 3rd Edition, Revised and Updated, May 1999 is incorrect

Q = [8.661 x 10^(-7) x d^(8/3) x S^(1/2)]/ n

it should be

Q = [1.123 x 10^(-5) x d^(8/3) x S^(1/2)]/n

Where

Q = discharge in cubic metre per hour
S = Slope
d = diameter of pipe in mm n= Manning’s coefficient of roughness

Regards
Linesh Chungath
India