How do you set up a pool booster pump for a cleaner or water feature?

A booster pump is a second, smaller pump that serves one feature — a pressure-side cleaner, waterfall, spa jets, or an in-floor manifold. It taps the return line, not suction, and only runs when the main pump is running. Size it to the feature's rated flow, interlock it with the main pump so it never runs dry, valve and union both ports, and install it below the water line. Skip the interlock and the seal smokes in the first minute.

How do you size a booster pump for spa jets?

Spa jets are commonly specified at 15 to 25 gpm per jet. Multiply that by the number of jets to get your total flow, then add about 20% margin on top. For a pressure-side cleaner you size to at least the GPM the cleaner manufacturer specifies at its rated head pressure — undersize it and you get a weak cleaner that wanders and gets stuck.

Why should you never tee a booster pump off the suction line?

The booster is supposed to tap the return line and take already-filtered, already-pressurized water. Teeing it off a suction line reduces main-pump flow and often cavitates the booster — that rumble, shaft-end vibration, and hot motor. It is one of the install-time mistakes that persists for the life of the pump, so the feed always comes off the return, never suction.

What makes a booster pump seal fail from running dry?

Running the booster with no main-pump flow. The main pump fails or loses prime, but the booster keeps running on its schedule with nothing to draw from — the seal smokes in the first minute. It is one of the two predictable failure modes I see in Florida. The permanent fix is a flow switch or a controller interlock so the booster physically cannot start without flow present.

Where should a booster pump be mounted relative to the pool?

Below the pool water line wherever you can manage it. That gives you flooded suction, which keeps the pump primed. Add a check valve on the inlet so it does not back-drain when it shuts off, unions at both ports because you will service it, and dedicated shut-off valves on both sides so it can come out without draining the whole system.

How do you protect a coastal booster pump from salt corrosion?

A coastal booster takes the same beating as your main pump. Specify stainless hardware when it goes in, and rinse the cabinet on every service. Salt corrosion is one of the three failure modes I see down here, right alongside dry-run seal loss and cavitation. Take the extra time on install and it runs unnoticed for a decade instead of rotting out early.

Pool Equipment Guide: Pumps, Filters, Heaters & Salt · 6 min read · By Matt Balog

Booster Pump Setup: Where It Fits, How to Size It, and Why They Fail

Booster plumbing sequence, sizing by feature type, main-pump interlocks, and the Florida failure modes.

By Matt Balog, Founder & Lead Pool Technician · Updated July 4, 2026 · 6 min read

Quick answer

A booster pump is a second, smaller pump dedicated to one feature — a pressure-side cleaner, waterfall, spa jets, or an in-floor manifold — and it runs only when that feature is active.
Tap the return line, never the suction line — the booster takes already-filtered, already-pressurized water; teeing off suction cuts main-pump flow and often cavitates the booster.
The main pump must run whenever the booster runs — without it the booster has nothing to draw from, so interlock the two with a time clock, controller, or return-line flow switch.
Size to the feature's rated flow — match the cleaner's specified GPM at head, size waterfalls by designed flow, and figure spa jets at 15–25 gpm each plus 20% margin.
The two classic Florida failures are dry-run seal loss and cavitation — both are install-time mistakes that a flow-switch interlock and a properly-sized feed line prevent.
Install it below the water line with a check valve, unions, and shut-off valves — flooded suction keeps it primed and you can service it without draining the system.

A booster pump is a second, smaller pump dedicated to a single feature: a pressure-side cleaner, a waterfall, a spa jet system, or an in-floor cleaning manifold. It runs only when that feature is active. Booster pumps fail in two predictable ways — seal failure from dry running, and cavitation from undersized feed — and both are install-time mistakes that persist for the life of the pump.

Where boosters fit in the hydraulics

The main circulation pump handles filtration and chemistry. The booster pump taps the return line (not the suction line) and takes already-filtered, already-pressurizedwater to boost it further for the feature. Typical plumbing:

Main pump suction → filter → heater (if present) → tee off the return line
Tee sends a branch to the booster pump inlet via a dedicated valve
Booster pump discharges through its own line to the feature (cleaner wall port, waterfall, etc.)

The main pump must be running whenever the booster is running. Without the main pump, the booster has nothing to draw from.

Sizing and matching

Pressure-side cleaners— the cleaner manufacturer specifies GPM at a given head pressure. Size the booster to deliver at least that. Under-sized boosters produce weak cleaners that wander and get stuck.
Waterfalls and sheer descents— size by the feature's designed flow. Too little flow = pathetic trickle; too much = splash and noise.
Spa jets— commonly specified at 15–25 gpm per jet. Multiply by the number of jets for total flow, then add 20% margin.

Control: how the booster actually gets power

The booster must always be interlocked with the main pump — running a booster without main-pump flow destroys the seal in seconds. Three common approaches:

Time clock slaved to main— simplest residential setup; both pumps share a timer, booster activates during a feature-run block.
Automation controller— controller schedules both and enforces main-on-before-booster-on as part of its logic.
Flow switch interlock— a flow switch on the return line physically prevents the booster from starting if no flow is present. Belt and suspenders, used on commercial installs.

Installation notes that prevent the classic failures

Install the booster below the pool water linewhere possible — flooded suction keeps it primed.
Check valve on the booster inlet— prevents back-drain when the unit shuts off.
Dedicated shut-off valves on both sides so the booster can be serviced without draining the whole system.
Unions at both ports— you will service the pump; plan for removal.
Never tee the booster off a suction line. Reduces main-pump flow and often cavitates the booster.

The commonly-seen Florida failure modes

Booster ran dry. Main pump failed or lost prime; booster kept running per schedule. Seal smoked in the first minute. Adding a flow switch or controller interlock is the permanent fix.
Booster cavitating. Rumble, shaft-end vibration, hot motor. Usually an undersized feed line, a partially-closed feed valve, or flow starvation when the main pump is at low RPM.
Salt corrosion. Coastal boosters take the same beating as main pumps. Specify stainless hardware on install; rinse the cabinet on every service.

A booster pump you never have to think about is one that was installed by someone who thought hard about it. The easy fail is plumb it in, schedule it, walk away. Take an extra hour to interlock, valve, and size it right and it will run unnoticed for a decade.

Frequently asked questions

No. The booster taps the return line and takes water the main pump has already filtered and pressurized. Without the main pump running there is nothing for the booster to draw from, so it will run dry. Run a booster without main-pump flow and the seal is destroyed in seconds — that is why the two pumps always have to be interlocked.