The friction loss in hydraulic can be evaluated through the use Of various flow coefficients. one such coefficient is the Hazen-Williams C factor. This factor for PVC & CPVC plastic piping system has been set at at C=150. The following formulae express the friction loss in feet of water and the water velocities in feel per second.

where,
f = friction head loss in feet of water per 100 feet of pipe.
C = constant for inside pipe roughness ( c=150 for extruded smooth wall thermoplastic pipe ).
Q = flow in us gallons per minute.
di = inside diameter of pipe in inches.

The value of c 150 for thermoplastic pipe is based on engineering measurements made with new and used thermoplastic pipe in several laboratories. Thus the value of c = 150 has a conservative bias. Using c = 150 the equation reduces to

Water velocities in feet per second v may be calculated as follows

Typical values of the Hazen Williams coefficient
Water Hammer_Pressure surge

Maximum pressure caused by water hammer May be calculated with the following formulae.

Where,
P = pressure surge (psi)
A = wave velocity (ftsec)
V = maximum velocity change (ftsec)
G = acceleration of gravity (32.2 ft sec²)
K= fluid bulk modulus (300 000 psi for water)
Di = pipe inside diameter (inches)
E = modulus of elasticity of the pipe (420 000 psi for PVC 360 000 psi for CPVC)
t = wall thickness (inches)