NFPA 1142 Rural Water Supply
Minimum on-site water supply Q = (V * occupancy * construction) / 5 per NFPA 1142 §5.
Example
You enter
- Building volume (ft³; footprint x avg ceiling) 30000
- Occupancy Hazard Classification (NFPA 1142 §5.2, OHC 3-7) 7
- Construction class (NFPA 1142 §5.2.7) V
- Exposure within 50 ft false
- UL-listed sprinkler system present false
You get
- Required minimum fire-flow (gal) 6429
Details, formula, and sources
With 1.5x exposure and 0.5x sprinkler multipliers; recommended tanker trip count.
WS = (V * CCN) / OHC per NFPA 1142 §5 (Occupancy Hazard Classification Number OHC 3-7 divides; Construction Classification Number CCN 0.5-1.5). 1.5x exposure multiplier when adjacent structure within 50 ft. 0.5x sprinkler reduction when UL-listed system present.
NFPA 1142-2022 (Standard on Water Supplies for Suburban and Rural Firefighting) §5.
nfpa.org/freeaccess.
Estimate. AHJ and licensed fire protection engineer govern.
Field names used by the API: volume_ft3, occupancy_class, construction_class, exposure_within_50_ft, sprinkler_listed, Q_min_gal
- Occupancy factors NFPA 1142 §5.2 Occupancy Hazard Classification Number (OHC 3 severe to 7 light; a divisor)NFPA 1142-2022 §5.2
- Construction factors Class I-V per NFPA 1142 §5.2.7NFPA 1142-2022 §5.2.7
- Exposure multiplier 1.5x when adjacent structure within 50 ftNFPA 1142-2022 §5.4
- Sprinkler reduction 0.5x contingent on confirmed UL-listed systemNFPA 1142-2022 §5.5; AHJ inspection governs
- Standard tanker sizes 1000 / 1500 / 2000 / 3000 galcommon apparatus sizing