About Pressure Drop Calculation

Revit computes pressure losses in piping based on the geometry and roughness of piping, fluid density, and fluid dynamic viscosity.

Values for density and dynamic viscosity are specified in the Mechanical Settings dialog. Roughness is specified in the type properties for pipe/pipe fitting component families.

Revit uses the Darcy-Weisbach equation to compute pressure drop on pipe segments, fittings, and accessories. You can select from the following Darcy-Weisbach friction factor methods: Haaland or Colebrook.

For closed loop hydronic piping networks, Revit aggregates the total flow and pressure drop on the pump equipment in the pipe network to calculate the total pipe system loop critical path pressure drop. A closed loop hydronic piping network contains:

• A single source equipment component such as a boiler or chiller (optional)
• A single pump or circulator
• Any number of loads such as radiators or fan coil units
• Any number of pipe segments in the supply section and return section of the loop