Jockey Pump
The Pressure Maintainer

Layout essentials: suction gate valve → jockey pump → discharge check valve → isolation valve → discharge manifold into the overhead header. The 0–6 bar pressure gauge upstream and the tap for the pressure switch on the control panel tell the jockey when to start and stop.

The Problem It Solves

A sprinkler system is never perfectly leak-free. Air bleeds out of fittings, a waterflow switch may weep, a small crack in a gauge adapter slowly drops pressure. Without anything to push back, system pressure slowly falls — and eventually the main fire pump starts, runs for thirty seconds, pressurizes the system, and shuts off. Then the leak drops pressure again. On it goes: start, stop, start, stop.

That churning is bad for the fire pump's bearings, seal assembly, and controller contactors — and it is catastrophic for a diesel-driven fire pump, where NFPA 20 limits the number of automatic start attempts. Short-cycling can exhaust the attempt sequence and lock the pump out. NFPA 20 solves it with a much smaller pump — the jockey — that runs whenever pressure drops even slightly, replenishes the leak, and shuts off before the main pump ever sees a demand.

Terminology — “Jockey Pump” vs. “Pressure Maintenance Pump”

Same device. NFPA 20 uses the formal term “pressure maintenance pump” throughout the standard body (§4.27 and elsewhere). “Jockey pump” is the universal industry / field term and appears in NFPA 20 Annex A. Cut sheets, controllers, and inspection reports use both interchangeably; some inspectors abbreviate to “PMP” or “JP.” If a drawing or spec calls it a “pressure maintenance pump,” it is a jockey pump — no difference.

Sizing & Setpoints — the 10-Minute Rule and the 10-PSI Rule

Capacity — aboveground sprinkler / standpipe systems

Per Kord Fire Protection's summary of NFPA 20 requirements, the jockey pump flow for an aboveground system “should be less than a single sprinkler head's discharge.” The design goal: let the main fire pump start whenever a sprinkler operates. This typically translates to 3–10 gpm depending on the system — small enough that even one open sprinkler overwhelms the jockey and forces the main pump to pick up Source 9.

Capacity — underground mains

NFPA 24 permits limited leakage in underground fire mains. For systems fed from underground service, NFPA 20 Annex A.4.27 sizes the jockey to make up the allowable underground leakage rate within 10 minutes, or 1 gpm minimum — whichever is greater. For these installations, the “1% of fire pump rated capacity” field shortcut is a defensible rule of thumb (a 1,500 gpm fire pump gets a ~15 gpm jockey) — but it is not the NFPA code requirement, and it overestimates on tight aboveground-only systems. Always cross-check with the actual measured or allowable leakage.

Discharge pressure

Sized for discharge pressure about 10 psi above the main fire pump churn (shutoff) pressure so the jockey is capable of maintaining a slight pressure dominance over the main pump when it is idle.

Setpoint stacking — the 10-PSI rule

Inverted setpoints (jockey start above jockey stop) make the jockey run constantly and never stop — a first-hour commissioning error that can burn out the motor the day it's energized. Always verify on startup with a calibrated test gauge.

Minimum-run timer

NFPA 20 Annex A.4.27 recommends a minimum run time of at least 1 minute after reaching the stop pressure. Without it, the jockey can short-cycle (on for 5 seconds, off for 30 seconds, 30 times an hour), which destroys motor windings from repeated locked-rotor inrush. All modern jockey pump controllers (Tornatech JP, Firetrol FTA-550J, Eaton) include the timer — check during inspection that it's actually set, not bypassed.

Typical Specifications

Vertical multi-stage packs high discharge pressure (200+ PSI) into a small footprint. Popular models: Grundfos CR, Goulds e-SV, Webtrol NV.

Sensing Line Requirements

Each jockey pump must have its own individual pressure sensing line, typically 15 mm (½ inch) nominal size, connected between its discharge check valve and its downstream isolation valve Source 9. The dedicated sensing line:

• Monitors system pressure accurately without interference from the main fire pump sensing circuit.
• Prevents false starts caused by pressure fluctuations elsewhere in the pump room or riser wall.
• Ensures precise response — the controller reacts to true system pressure changes, not transient hammer in the manifold.

Controllers — UL 508A, not UL 218

This is the single most important code distinction about jockey pumps: the jockey controller is NOT a fire pump controller.

NFPA 20 prohibits sharing one controller between the jockey and the main pump. They serve different roles, have different listing requirements, and different supervision requirements. An inspector finding a single combined panel is writing a deficiency.

Valve Arrangement & Optional Relief Valve

The standard valve arrangement around a jockey pump, visible in the labeled pump-room photo above:

• Suction isolation valve (OS&Y gate) — upstream of the pump, allows service without shutting down the whole fire main.
• Jockey pump — vertical multistage in the photo above.
• Discharge check valve — prevents system water from backfeeding through the pump during main fire pump operation (when discharge pressure from the main pump exceeds the jockey shutoff).
• Discharge isolation valve (gate or butterfly) — downstream of the check valve, bracketing the pump for maintenance.
• Pressure sensing tap — ½" NPT tap between the check valve and the discharge isolation valve, feeding the jockey controller's pressure switch.
• Drain valve — used to drain the pump and its associated trim for service.
• Relief valve (optional but recommended, per 119firecontrol) — protects the pump and local piping from over-pressurization if the pressure switch fails in the closed/stuck-on position and the pump keeps running against a closed discharge. Not universally required, but cheap insurance on vertical multistage units that can push well above their rated shutoff Source 10.

Failure Modes — What Actually Breaks

DO NOT — Common Installer & Operator Errors

NFPA 25 ITM Notes

NFPA 25 does not prescribe a separate test program for the jockey pump the way it does for the main fire pump. The jockey is exercised passively every time system pressure fluctuates, which means it gets dozens to hundreds of operational cycles per week. That said, during weekly/monthly visits and annual tests, verify:

• Weekly: visible running-pilot light, no leaks at pump base, suction and discharge gauges steady, no abnormal noise/vibration, starts per hour is reasonable (≤ a few).
• Monthly: functional start/stop test — open the inspector's test to drop pressure, verify jockey starts at the correct setpoint, runs for at least the minimum timer duration, stops at the correct setpoint.
• Annual (coordinated with main fire pump flow test): verify jockey isolates/bypasses correctly during the main pump churn / rated / peak test points without interfering with measurements. Verify setpoints against commissioning baseline and against the current main pump churn pressure.
• After any maintenance: vent the pump at the air-release port before restart (vertical multistage). Verify setpoints weren't changed. Record run-hours meter reading.

Jockey Pump vs. Fire Pump — Quick Comparison

Frequently Asked Questions

References