A jet pump is a centrifugal pump. That is the part most comparisons skip. Inside, it has the same spinning impeller as any other centrifugal. What makes it a jet pump is one extra assembly bolted on, an ejector, and it exists to pull water from further below the pump than a plain centrifugal can reach.
So the real question is not “jet or centrifugal”. It is how far below the pump the water sits, and what reaching it costs.
Start with one measurement: where does the water sit?
If the water is above the pump, or level with it, gravity feeds it for you. That is a flooded suction, and a plain centrifugal is the right tool. A tank with a bottom outlet, a pond, a pool, a header tank on a stand: all flooded suction.
If the water sits below the pump, the pump has to lift it, and that is where the ceiling turns up. No pump sucks water. It drops the pressure at its inlet and lets the atmosphere push water up the pipe. At sea level, air pressure can only hold a column of water about 10.3 metres high, and that is the perfect-world figure: no friction, no warm water, no air leaks. In practice a plain centrifugal runs out of puff around 6 to 7 metres, less on a hot day.
What the ejector actually buys you
The ejector is a nozzle and a venturi. The pump sends part of the water it has already pressurised back down through that nozzle. Forcing it through the restriction speeds it up and drops its pressure, dragging more water in behind it.
Shallow-well jet: the ejector sits on the pump body, one pipe runs down to the water, and it handles lifts of roughly 7 to 9 metres.
Deep-well jet: the ejector goes down the bore on twin pipes, one feeding it, one carrying water back. With the ejector down near the water doing the hard part, it works at 25 metres and beyond.
Jet pumps also hold prime well. With the casing full and a decent foot valve at the bottom, one normally restarts on its own. If yours keeps losing prime, that is a fault, and our guide to priming a water pump covers why.
What you give up for that suction
Efficiency. A jet pump recirculates part of its own output instead of delivering it, so every litre going back down the nozzle is a litre not coming out your tap. On the same power, a plain centrifugal with a flooded suction moves more water.
You also get noise. Jet pumps sit above ground with an air-cooled motor and a hard-working ejector, and they are not quiet neighbours. Read up on pump noise and vibration before mounting one under a bedroom window.
Then there is the flow ceiling. Jet pumps are built to lift, not to shift volume. If the job is plenty of water at low pressure, which is what a pond or waterfall wants, a jet pump is the wrong shape of tool.
Matching the pump to the job
Pond, waterfall or water feature: plain centrifugal, usually a submersible sitting in the water. Size it off pond volume and waterfall height, not motor watts.
Rainwater tank feeding garden taps or the laundry: a multistage centrifugal pressure pump beside the tank. The pump is gravity fed, so an ejector buys you nothing.
Buried tank or sump: self-priming centrifugal inside that 6 to 7 metre band, shallow-well jet past it.
Bore or well: measure the standing water level first, at the lowest it gets. Inside the band, a self-priming centrifugal or shallow-well jet does it. Deeper, and it is a deep-well jet against a submersible dropped down the casing. The submersible usually wins: it pushes rather than pulls, so depth barely troubles it, and it runs quieter.
Pool: a dedicated self-priming pool pump with a hair and lint basket, never a general-purpose jet pump.
The numbers to have before you buy
Suction lift: metres from the water surface up to the pump inlet, taken at the lowest the water gets.
Total head: suction lift, plus the rise on the delivery side, plus friction losses through the pipe run and every elbow in it.
Flow: litres per minute you actually need. Two taps at once is a very different number from filling a pond.
Duty: hours per day, and whether it will be stopping and starting constantly. Frequent short cycling wears a pump out fast.
Read those against the pump’s performance curve, not the headline figure on the carton. That number is usually maximum head at zero flow, or maximum flow at zero head, and you will never run at either.
Before you commit
Tying a tank or bore supply into household plumbing, and fitting any backflow prevention that applies, is regulated, and requirements vary between states and water authorities. Check with your local council or water authority, and have a licensed plumber do the connection. Hard-wiring is electrical work. Licensing sits with your state electrical safety regulator, and the AS/NZS 3000 wiring rules cover RCD protection, so anything past a plug into an existing outdoor outlet is a job for a licensed electrician.
And dry running kills pumps, jet or centrifugal.
Common questions
Is a jet pump more powerful than a centrifugal pump?
No. It lifts from deeper, which is a different thing. For the same motor size, a plain centrifugal on a flooded suction delivers more flow, because a jet pump spends part of its output driving its ejector.
Can I use a jet pump for a garden pond?
You can, but you should not. Ponds want high flow at low pressure and jet pumps are built for the opposite. A submersible pond pump moves more water for less power and far less noise.
The short version
Measure how far the water sits below the pump and it largely chooses itself. Level or above: plain centrifugal. A few metres below: self-priming centrifugal or shallow-well jet. Down a bore: deep-well jet or submersible.