How is head loss calculated in pressure pipe systems?

Head loss in pipes has friction and minor components. Darcy-Weisbach: hf = f*(L/D)*(V^2/2g), where f = friction factor from Moody diagram (function of Reynolds number and relative roughness). Hazen-Williams: V = 0.849*C*R^0.63*S^0.54, where C = roughness coefficient (150 for plastic, 100 for old iron). Minor losses (valves, bends, fittings): hm = K*(V^2/2g). Energy equation with losses used for pipe system analysis. Hardy-Cross method iteratively solves pipe network problems.