By combining equations (1) and (2), v is obtained directly:--

v = [root](gdi/2[zeta]) = [root](g/2[alpha]) [root][di/{1 + 1/12d}]. (4)

For new pipes [root](g/2[alpha]) = 56.72

For incrusted pipes = 40.13

For pipes not less than 1, or more than 4 ft. in diameter, the mean

values of [zeta] are

For new pipes 0.00526

For incrusted pipes 0.01052.