Sprinkler Hydraulic Calculator

Back-calculates a wet-pipe sprinkler system from the most-remote sprinkler (at the required residual pressure) inward through the branch line, cross-main, and riser to the base-of-riser total demand, then checks delivered density against the occupancy hazard class.

Single-pass NFPA 13 §23.4.3 walk (2013/2016 numbering — Ch. 23 is ESFR in 2022/2025; the current equivalent is not yet confirmed): starting at S1 (most-remote sprinkler, given pressure), each upstream sprinkler's pressure is recovered by adding the Hazen-Williams friction + elevation loss of the intervening pipe segment to the previous pressure, then re-evaluating Q=K√P — repeated sprinkler-by-sprinkler along the branch, then symmetric-branch-by-branch along the cross-main, then along the riser to the base. Hose-stream allowance is added at the base of riser only (excluded from the density check).