Josep Sorribes Monros asked which formula EPANET uses to compute
the Darcy-Weisbach friction factor for turbulent flow. EPANET uses the
Swamee and Jain equation which is an explicit approximation to the
implicit Colebrook-White equation. For more details on equations for the
friction factor, see "Analysis of Flow in Water Distribution Networks" by
P.R. Bhave (Technomic Publishing, 1991).

Lew Rossman