The Simple Hydraulic Calculator has many features to help you properly design an automatic sprinkler system:

Hazen-Williams friction loss formula as per NFPA 13

Supply and Demand Calculations

Multiple water sources supported

Multiple booster pumps supported

Multiple backflow preventers / fixed loss valves supported

Suitable for wet, dry, pre-action, deluge, and water-foam systems

Velocity pressures or total pressures

Model tree, grid, loop, and custom systems

Hardy-Cross method of analysis (in use for over three years)

Optional Newton-Raphson method of analysis (currently in beta)

Metric or U.S. units and conversion

Supports over 32,000 pipes

Supports over 32,000 nodes

Use descriptive pipe and node names up to eight characters long

Automatic peaking of grid, tree, and looped systems

Automatic fitting equivalent length adjustment

Editable pipe materials database

Negative pressures allowed

Negative elevations allowed

'Old school' data entry (faster for many than dialog based data entry)