EPANET hydraulics engine computes headlosses along the pipes by using one of the three formulas:
*Hazen-Williams formula: used to model full flow conditions under simplified conditions (turbulent flow, temperature around 60 degrees Fahrenheit, and viscosity similar to water) https://www.epa.gov/water-research/epanet
*Darcy-Weisbach formula: used to model pressurized flow under a broader range of hydraulic conditions
*Chezy-Manning formula: used to model pressurized flow by using Chezys roughness coefficients for Mannings equation
Since the pipe segment headloss equation is used within the network solver, the formula above is selected for the entire model.