10.3 Pressure-Maintenance Pumps: Purpose, Capacity, and Coordinated Settings

The pressure-maintenance function

A pressure-maintenance or jockey pump handles small pressure losses so that the main fire pump does not start for every minor fluctuation. It is not credited as the required fire pump supply. Its flow and pressure must fit the actual installation, including leakage, pressure range, equipment ratings, and the need for the main pump to respond to a fire demand. Do not apply a universal percentage of main-pump capacity as though it were a complete NFPA sizing calculation.

Small losses can come from temperature change, leakage, or equipment operation. Repeated jockey-pump starts are useful diagnostic information. They do not prove that every loss is harmless. A new underground leak, leaking check valve, open test connection, or damaged seal may require correction. Review the pattern and investigate the cause rather than simply raising the cut-out pressure or fitting a larger pump.

Capacity and pressure are separate

A jockey pump must have enough capacity to manage the intended small losses and enough pressure capability to reach its stop setting. A 1% capacity rule is sometimes used as a preliminary heuristic, but it is not a universal mandatory requirement and does not establish the appropriate pump for every system. The actual installation and NFPA 20 provisions govern. Avoid selecting a pump so large that it masks the demand that should initiate the main fire pump.

Pressure capability also matters. If the selected pump cannot reach its cut-out setting at the actual suction condition, it may run continuously and overheat. Compare the pump curve and supply with the required operating range. A label showing a high maximum pressure is not proof that the pump supplies the needed flow at that pressure. Conversely, a pressure-maintenance pump that reaches cut-out does not establish that the main fire pump meets its demand curve.

Coordinate start and stop settings

The normal sequence gives the jockey pump an opportunity to restore a small pressure loss before pressure reaches the main fire pump's starting point. Multiple fire pumps can have coordinated sequential starting settings. Use the approved settings, system requirements, controller capabilities, and applicable NFPA 20 guidance. Do not label one “symmetrical” set of offsets as mandatory for every installation or casually lower a main-pump start point to suppress nuisance starts.

For an arithmetic example only, assume approved settings of 165 psi jockey stop, 150 psi jockey start, and 140 psi main-pump start. The jockey operating differential is 165 − 150 = 15 psi, and the separation between jockey start and main-pump start is 150 − 140 = 10 psi. These numbers illustrate the order and differences. They are not independent design approval for another building, and component maximum working pressure must still be respected.

A reversed sequence can cause nuisance main-pump starts. If the main pump starts at 155 psi and the jockey pump starts at 150 psi, falling pressure reaches the main-pump setting first. Diagnose the actual settings and cause. Do not merely relabel the gauges or leave the main controller off to keep it quiet.

Main-pump stopping is a distinct function

A jockey controller ordinarily starts and stops automatically for pressure maintenance. Main fire pump controllers have their own NFPA 20 stopping requirements and permitted automatic-stop arrangements. Manual stopping is a key fire pump function, but an inspector should not claim that all approved automatic stopping is prohibited or limited to a fictional universal site category. Verify the actual approved controller configuration, required minimum run time where applicable, and manufacturer procedure.

A pressure recovery during firefighting can be temporary. Controller stopping logic must not be changed casually because the system has reached churn pressure. An annual test should verify the prescribed behavior, not teach a new control strategy. Document unexpected stopping, failure to stop as prescribed, or a controller left in an incorrect mode and arrange appropriate correction.

Observe the sequence safely

Plan the test with the owner and monitoring service, verify normal valve positions and discharge capacity, and use a controlled test connection. Record starting pressure, jockey start/stop observations, main-pump start, and the applicable controller status. Use calibrated instruments appropriate to the measurement; an imprecise installed gauge can make adjacent settings appear identical.

Any temporary isolation or controller-mode change must follow the approved procedure and impairment plan. Keep a clear list of altered positions so restoration is verified. Do not perform exposed energized controller adjustments during routine ITM. Use external controls as intended and refer other work to qualified personnel. A technician should not defeat alarm supervision simply to keep the test quiet.

Afterward, restore automatic mode, normal sensing and supply paths, and all valve positions. Check for leaks, overheating, unresolved cycling, and abnormal indications. Confirm that monitoring is normal and that responsible parties know the final status. Preserve the measured values for comparison at the next visit. If a pump cycles more often than before, a trend record can help distinguish a pressure-setting issue from a developing leak.

Sources checked October 19, 2026: NFPA 20 (2022), pressure-maintenance and controller provisions; NFPA 25 (2023), Chapter 8.