Standpipe Friction Loss
Riser elevation plus per-outlet friction.
Example
You enter
- Riser height (ft) 200
- Outlet count 1
- GPM per outlet 250
- Outlet hose length (ft) 100
- Outlet hose diameter 2.5_in
You get
- Elevation pressure 86.8 psi
- Hose friction (one line) 12.5 psi
- Per outlet (psi) 12.5
- Total 99.3 psi
Checked against published worked examples from: NFPA 14 (2024) standpipe hydraulics.
Details, formula, and sources
Formula or tableTotal = elevation (0.434 psi/ft × height) + friction in one outlet's hose line (NFA CQ²L). Lines on separate outlets run in parallel, so their friction does not add; the riser carries their combined flow, n × Q. Riser-pipe friction and the valve/appliance loss are not included. Min residual at the topmost outlet 100 psi for Class I per NFPA 14 §7.8 (Minimum and Maximum Pressure Limits; §7.10 is flow rates).
Source and editionNFPA 14 (2024) §7.8 (Minimum and Maximum Pressure Limits) and §7.10 (Flow Rates) by name and section.
Free accessNFPA 14 read-only at nfpa.org/freeaccess.
What governsEstimate. AHJ and licensed fire protection engineer govern.
API field namesriser_height_ft, outlet_count, gpm_per_outlet, outlet_length_ft, hose_diameter, elevation_psi, friction_total_psi, per_outlet_psi, total_psi
- Class I min residual 100 psi at the topmost outletNFPA 14-2024 §7.8