JavaScript must be enabled in order to use this site.Please enable JavaScript in your browser and refresh the page. Engineer’s Reference This section provides you with tables of commonly used roughness values and fitting loss coefficients. Roughness Values-Manning's Equation Roughness Values-Darcy-Weisbach Equation (Colebrook-White) Roughness Values-Hazen-Williams Equation Typical Roughness Values for Pressure Pipes Fitting Loss Coefficients Parent topic: Technical Reference