What is a Circulating Pump & How Does it Work?

If you’ve ever worked with a closed-loop system (think HVAC, hydronic heating, or certain industrial process loops) you’ve probably come across a circulating pump. These compact pumps are quite essential for keeping things moving behind the scenes.

First Things First: What is a Circulating Pump?

A circulating pump (sometimes called a circulator pump) is a type of pump used to move fluid within a closed system. The key here is closed system – you’re not pulling in outside water or sending fluid to a drain. Instead, the pump helps recirculate the same liquid to maintain consistent flow, pressure, and temperature.

In HVAC systems, this could mean circulating hot water from a boiler to radiators or chilled water in a cooling loop. In industrial setups, a circulating pump might be keeping process fluid at a stable temperature or moving it through a filtration system.

It’s not about volume like you’d see with a high-flow dewatering pump. It’s about keeping the loop moving efficiently and reliably.

How Does a Circulating Pump Work?

At a basic level, a circulator pump is a type of centrifugal pump. It uses a spinning impeller to create pressure and move fluid through the system. Because the system is closed (meaning the same fluid is reused), these pumps don’t need to lift water or draw from a supply. They’re focused on keeping things moving.

Here’s the general idea:

1. The pump pulls fluid in through an inlet.
2. The impeller adds kinetic energy to the fluid.
3. That energy is converted to pressure, forcing the fluid through the discharge side and into the system.

Since it’s a loop, the fluid returns to the pump, and the cycle continues.

TIP: Circulating pumps aren’t made for higher pressures. If your system needs to move fluid across long distances or large vertical changes, you’ll want a different kind of pump.

Where Are Circulator Pumps Used?

You’ll find circulators in a variety of places…some more obvious than others:

• Hydronic heating systems – Moving hot water from a boiler to radiators or underfloor heating
• Chilled water systems – Recirculating water in cooling loops for AC or industrial chillers
• Solar thermal systems – Keeping heated water or glycol moving from solar collectors to storage tanks
• Process systems – In industrial settings, circulators help maintain temperature or move fluid between system components
• Domestic hot water recirculation – Preventing long waits at the tap by keeping hot water circulating near fixtures

Circulating Pumps vs. Booster Pumps

It’s easy to confuse circulator pumps with booster pumps, but they serve different purposes. Circulating pumps keep fluid moving in a closed system. Booster pumps increase pressure in an open system (like municipal water supply lines).

What Makes a Good Circulating Pump?

It’s not all about horsepower or flow rate. With circulating pumps, efficiency and reliability are usually more important than brute strength. A good pump runs quietly, resists corrosion, and stays consistent even after thousands of hours of operation.

Key Factors to Look At:

• Flow Rate – How much fluid is moving through the loop?
• Head Pressure – How much resistance does the system have?
• Material Compatibility – Is the fluid corrosive or high-temp?
• Pump Type – Inline, end suction, close-coupled… the design affects footprint and maintenance.
• Motor Efficiency – ECM motors are common for their energy savings in smaller systems.

Tips from Pump Experts

Here’s some quick advice we’ve picked up after years in the pump business:

• Don’t oversize the pump. Bigger isn’t better, and too much flow can be just as problematic as too little, especially in closed systems.
• Always check system head before specifying. A loop that seems simple can hide a lot of friction loss.
• Pay attention to noise. Circulators are usually quiet, so if it’s buzzing or knocking, something’s off.
• Match materials to the fluid. Corrosion or scale buildup can quietly kill a circulator pump over time.

Circulator pumps are generally low-maintenance, but they’re not maintenance-free. Over time, seals can wear out, bearings can go bad, and buildup from poor water quality can gum things up.

Work With a Pump Partner Who Gets It

Circulating pumps may be small, but they’re a big part of many systems running reliably day after day. If you’re unsure which pump fits your system or just want to upgrade for better efficiency, PumpWorks is here to help.

We’re more than just a pump manufacturer or supplier. We work with you to understand your system’s flow demands, operating conditions, and control needs to recommend a solution that performs well without overcomplicating things. At PumpWorks, we help customers spec the right pump for the right job…not just whatever’s on the shelf.

Need help picking the right pump or want to troubleshoot your current setup? Reach out, we’re happy to help.