Bell & Gossett PL Series Booster Pumps: Sizing and Selection Guide

Booster pumps get lumped in with circulators a lot, but they're solving a different problem. A circulator moves water around a closed loop against relatively low resistance. A booster pump exists to raise pressure, getting water up to a higher floor, through a long horizontal run, or to a fixture that isn't getting enough pressure on its own. Bell & Gossett's PL Series is built specifically for that job, in a compact in-line package.

What Makes a Booster Pump Different

The core distinction is what the pump is actually working against. A circulator overcomes friction loss in a loop where the water eventually comes back around. A booster pump adds real pressure to push water somewhere it wouldn't reach on its own, against elevation, distance, or a fixture that needs more pressure than the base supply provides. The PL Series is designed as a maintenance-free, in-line unit, meaning it installs directly into the pipe run rather than needing a separate base and coupling like a larger end-suction pump.

The PL Series Lineup

Bell & Gossett offers the PL Series across a range of horsepower and speed combinations to match different pressure-boosting needs:

• PL-30 — 1/12 HP, 2650 RPM. The smallest unit in the line, suited to lighter-duty boosting applications.
• PL-36 — 1/6 HP, 3300 RPM. A step up in both horsepower and speed for moderate boosting needs.
• PL-45 — 1/6 HP, 3300 RPM. Same motor spec as the PL-36, sized differently for higher flow or head requirements at that power level.

All three ship as cast iron, dry-motor construction with 2-bolt flange connection ports, sold less flanges (the flanges themselves are ordered separately to match your specific piping).

Sizing: Pressure Requirement First

Booster pump sizing starts with a different question than circulator sizing does. Instead of matching GPM and head loss around a loop, you need to know how much additional pressure the application actually requires: the difference between your base supply pressure and what the fixture or system needs to see. That pressure deficit, combined with your required flow rate, determines which PL model actually delivers what you need. A pump sized only by flow rate without checking the pressure boost requirement can leave you with adequate volume but still-inadequate pressure at the point of use.

Dry-Motor Construction: What It Means for Maintenance

The PL Series uses dry-motor construction, where the motor is mechanically sealed off from the pumped fluid rather than being lubricated by it (the way a wet-rotor circulator works). This trades a small amount of efficiency for a maintenance-free design with no shaft seal to wear out and leak over time, one of the reasons Bell & Gossett markets this line specifically as low-maintenance.

Installation Notes

• Flanges are sold separately on all three models. Confirm you're ordering the correct flange size and rating to match your piping before installation, not just the pump body.
• In-line orientation means the pump installs directly into the pipe run. Confirm your piping layout has adequate support on both sides of the pump, since it isn't base-mounted like a larger end-suction unit.
• Electrical connection should be confirmed against the pump's actual nameplate rating (115V/1-phase/60Hz across this line) before final hookup.

National Boiler Supply carries the full Bell & Gossett PL Series booster pump line. Reach out with your required pressure boost and flow rate and we'll help you match the right model.