Technical Guide to the Booster Pump
What a booster pump is, how to size it for cistern-to-rooftop-tank transfer, and how it differs from the fire system pumper connection.
TL;DR
A booster (transfer) pump moves water from a lower to a higher level — typically from the cistern to the building rooftop tank. In Brazilian practice, a horizontal centrifugal pump with automatic start by level switches.
The Brazilian fire-system "registro de recalque" is NOT a pump: it is the sidewalk fire department connection (NBR 13714). The fire system pump is the main + jockey set, per NBR 16704/NFPA 20.
Sizing uses four data points: flow (daily volume ÷ desired pumping time), geometric height between levels, piping friction losses and available NPSH at suction.
Building designs use a duplex set — one duty pump and one standby in automatic alternation — so a single unit failure never leaves the building without water.
FB Bombas serves building and industrial transfer duty with the FBCN series (standardized centrifugal), manufactured in Cabreúva, Brazil since 1944, with flows up to 2,200 m³/h and head up to 135 m.
A "bomba de recalque" (transfer pump) moves volume vertically — it draws from the cistern and fills the rooftop tank, controlled by a level switch. A "booster" or "pressurizer" pump raises pressure directly in the distribution network, controlled by a pressure switch or VFD. Different functions, different installation points. In large-scale industrial applications, normalized centrifugals such as the FBCN series cover both cases.
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What is a bomba de recalque (transfer pump)?
A bomba de recalque (transfer pump) moves water from a lower level to a higher one; in a building, from the cistern to the rooftop tank. The name comes from the recalque (discharge) piping installed after the pump. The typical building configuration is a horizontal centrifugal pump controlled by level switches.
How to size a building transfer (recalque) pump?
Calculate Q = volume to transfer ÷ pumping time, in consistent units. Calculate TDH = geometric height + friction losses, check the available NPSH and select the model on the manufacturer’s curve. The design also defines controls and redundancy.
Which pump for building water transfer duty?
The classic configuration is a horizontal clean-water centrifugal pump; at FB, the family is FBCN. The 2,200 m³/h and 135 m limits belong to the series catalogue, not to the building design. The exact model depends on flow, total head and NPSH.
Does a transfer pump need a standby unit?
Consolidated building practice uses two equivalent pumps, one on duty and one on standby, with automatic alternation. This balances running hours and keeps supply after a unit failure. In industrial service, redundancy must follow criticality and the project.
Is the fire department connection the same as a transfer pump?
No. The recalque connection (fire department connection) is the passive inlet through which the fire brigade injects water into the hydrant network, per the NBR 13714-based design. The building transfer pump moves water between reservoirs; they are distinct pieces of equipment in distinct systems.
What is the difference between a transfer pump, a pressurizer and a jockey pump?
The transfer (recalque) pump fills the rooftop tank and is controlled by level; the pressurizer raises pressure in the consumption network and is controlled by a pressure switch or VFD. The jockey maintains fire-network pressure and belongs to the set governed by NBR 16704/NFPA 20. Function, control and network are not interchangeable.
What Is a Booster Pump?
Definition, the double meaning of the term and where each applies
A booster (transfer) pump moves water from a lower level to a higher level — in the typical building installation, from the cistern (lower tank) to the rooftop tank. In Brazilian practice the discharge piping after the pump is called the "recalque" line, as opposed to the suction line before it. In most buildings it is a horizontal centrifugal pump, operating in automatic cycles commanded by level switches.
Mind the double meaning: in the fire-fighting system there is the Brazilian "registro de recalque" — the sidewalk fire department connection through which the fire truck injects water into the hydrant network. Despite the name, it is not a pump. Whoever is looking for the fire system pump actually needs the main fire pump and the jockey pump, governed by NBR 16704 and NFPA 20.
Transfers water from the cistern to the rooftop tank
Horizontal centrifugal — FBCN series for clean water
Automatic start by level switches (float)
Duplex set: 1 duty + 1 standby in alternation
How to Size It
The four data points that define the correct booster pump
Design flow
Daily consumption volume divided by the desired pumping time. Common building practice: the pump replaces the day’s consumption in a few operating hours instead of running continuously.
Total head
Geometric height between cistern level and rooftop tank inlet, plus friction losses from piping, fittings and valves. The data point most often wrong in catalog-only budgets.
Available NPSH
Suction must deliver enough pressure so the pump does not cavitate — deep cisterns or long suction lines require NPSH verification before purchase.
Alternating standby
Building good practice: two identical pumps, one duty and one standby, with automatic alternation at the control panel — a single failure never leaves the building without water.
Booster vs. Pressure System vs. Jockey
Three building pumps with similar names and different functions
| Criteria | Booster | Pressure set | Jockey |
|---|---|---|---|
| Function | Fill the rooftop tank | Keep pressure in the consumption network | Keep pressure in the FIRE network |
| Control | Level switches (float) | Pressure switch or VFD | Pressure switches with NFPA 20 setpoints |
| Duty | Long cycles, few times a day | Frequent, follows consumption | Short cycles, compensates micro-leaks |
| Reference standard | Building hydraulic design | Building hydraulic design | NBR 16704 / NFPA 20 |
Frequently Asked Questions
What is a booster pump?
A booster pump raises the pressure of a fluid already present in a line — installed in series in the distribution piping to increase pressure at the points of use. It differs from the bomba de recalque, which transfers volume from the cistern to the upper tank. In industrial applications, the FB Bombas FBCN series serves both functions, with flows up to 2,200 m³/h.
Why does my transfer pump start and stop all the time?
Short cycling on a float-controlled transfer pump usually indicates wrong level-switch adjustment (dead band too narrow between start and stop), a stuck float or a tank undersized for consumption. If it is a pressure-boosting pump (pressure switch), the typical cause is a discharged pressure tank or a switch with a narrow differential. Constant cycling kills motor life — fix the control before replacing the pump.
Does FB Bombas serve industrial transfer beyond buildings?
Yes. The same FBCN series that does building transfer serves industrial water transfer, cooling tower make-up, boiler feed and clean-water processes — with flows up to 2,200 m³/h and head up to 135 m, in 53 standardized models. For viscous fluids the indication changes to the gear series (FBE/FBEI), and for thermal oil, the FBOT.
Need a booster pump?
Send flow, head and duty (building or industrial). FB engineering sizes the ideal FBCN set — with alternating standby when the design requires it.
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