Jockey (Pressure-Maintenance) Pump Sizing (NFPA 20)
The jockey pump flow and the staggered pressure-switch settings for a fire-pump system, per NFPA 20 practice: jockey flow is small (about 1% of the fire pump's rated flow, at least 1 gpm) so it makes up leakage without the fire pump starting on every drop -- a 750 gpm fire pump takes about a 7.5 gpm jockey. The switches stagger so the jockey acts first: jockey stop = fire-pump churn (shutoff) pressure + minimum static supply (170 psi for a 120 psi churn and 50 psi static); jockey start = stop - 10 (160); fire-pump start = jockey start - 5 (155). A too-large jockey masks a real flow and fails to start the fire pump on a fire. A settings guide; NFPA 20, the pressure switches, and the AHJ / stamped fire-pump design govern.
Formula and source
jockey_gpm = max(0.01 x fire_pump_gpm, 1); jockey_stop_psi = churn_psi + min_static_psi; jockey_start_psi = jockey_stop_psi - 10; fire_pump_start_psi = jockey_start_psi - 5.
NFPA 20 (Standard for the Installation of Stationary Pumps for Fire Protection) pressure-maintenance (jockey) pump practice, by name; the pressure-switch settings and the AHJ govern.
Audience
This tile is built for fire-ground and the adjacent professions in the Fire-Ground Engineering group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.
Related tools
Posture
Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.