Choose a Well Jet Pump by Water Level and Ejector Setup

A well jet pump is an above-ground centrifugal pump that uses a nozzle-and-venturi assembly, called a jet or ejector, to draw water from a well. A shallow-well system has that assembly at the pump; a deep-well system places it down the well. A convertible pump can serve either arrangement, but only with the correct components. Goulds’ jet-pump manual describes these configurations.

The first selection question is not “How deep was the well drilled?” It is “How far below the pump does the water fall while pumping?” Then check the required flow, delivery pressure and piping losses.

How the jet moves water

The centrifugal impeller supplies pressurized drive water to a nozzle. The nozzle turns pressure into a fast-moving stream, creating a low-pressure suction chamber that draws in well water. The venturi then recovers some of the stream’s velocity as pressure.

In a deep-well arrangement, one passage sends drive water down to the ejector, and another returns the mixture of drive water and newly drawn well water to the surface pump. Part of that mixture recirculates; the net water drawn from the well supplies the house. This recirculation explains why gross flow through the pump is not the same as useful household output. Goulds’ technical manual explains the flow paths and pressure recovery.

Identify the arrangement before buying

Arrangement	Ejector location and water path	Main selection constraint
Shallow-well jet	Built into the pump or attached as an adapter; one suction pipe to the well	Effective suction lift must remain within the model’s limit
Twin-pipe deep-well jet	Ejector down the well; separate drive and return pipes	Pump, ejector, pipe sizes and pressure-control setting must work together
Packer deep-well jet	Ejector down the well; the space between the suction pipe and casing carries drive water	Casing dimensions, condition and packer sealing matter

These arrangements appear in Goulds’ installation manual. A packer system is the important exception to identifying a deep-well jet solely by two separate pipes inside the casing.

“Convertible” does not mean that a shallow-well-only pump becomes a deep-well pump by adding more pipe. For a replacement, record the existing pump model and, from installation records if available, the ejector’s nozzle and venturi identifiers—not just motor horsepower. If the down-well components are unknown, ask the installer how compatibility will be established. Pentair’s jet-kit instructions list different nozzle-and-venturi combinations and direct installers to model-specific performance and depth-setting information.

What the 25-foot limit actually means

Goulds specifies a maximum shallow-well suction lift of 25 feet, including vertical lift plus suction-pipe friction loss. Pentair likewise bases shallow-versus-deep selection on the distance from the pump to the water while the pump is running—not the resting water level. Goulds; Pentair.

For example, an illustrative 21-foot pumping lift plus 5 feet of calculated suction loss gives 26 feet of effective lift. That is outside the stated 25-foot limit even though the water itself is only 21 feet below the pump. Horizontal distance adds friction, not vertical elevation.

Altitude also reduces the atmospheric pressure available to push water into the suction chamber. Near the limit, do not treat 25 feet as guaranteed capability at every site; check the manufacturer’s applicable performance data and altitude guidance. Goulds’ technical manual explains atmospheric-pressure-driven suction and tabulates pressure at different elevations.

Match flow and pressure—not horsepower alone

For a shallow-well jet, read the exact pump’s performance table at the total suction lift and required discharge pressure. For a deep-well jet, use the matched pump-and-ejector data, checking the specified jet setting depth, pumping water level, pipe losses and drive-pressure requirement. Goulds provides model-specific ejector and control-valve settings and explains offset-pipe loss allowances. A maximum-flow number cannot establish what the system will deliver at household pressure.

For illustration, Goulds’ May 2020 JS+ brochure gives these ratings at 20 feet of total suction lift:

Model	Motor rating	Output at 40 PSI	Output at 50 PSI
J5S	½ HP	7.1 US GPM	2.3 US GPM
J5SH	½ HP	6.8 US GPM	5.8 US GPM

The two motors have the same horsepower, but their higher-pressure output differs substantially. These are a worked comparison from the manufacturer’s dated performance table, not a blanket recommendation for either model. Use the applicable data for the replacement being offered.

For a conventional pressure-switch system, also verify that the pump can reach the switch’s cut-out pressure at the expected water level. In deep-well jet systems, distinguish the jet pressure-control valve, which maintains drive-water pressure, from the pressure switch, which starts and stops the motor. Goulds warns that inadequate jet backpressure can cause loss of prime during heavy demand. Installation manual.

Size the pressure tank separately by usable drawdown and required motor runtime; nominal tank gallons are not usable water storage. See bladder-tank sizing by drawdown.

Keep the jet system or consider a submersible?

Keeping a jet system is worth considering when the pumping level suits it and the existing piping and ejector are serviceable. The surface motor and pump remain accessible, although a deep-well ejector still requires down-well work.

Where the casing and installation permit, compare a submersible before replacing a deep-well jet like for like. Its pump and motor operate underwater, it needs no manual priming, and it avoids the jet’s drive-water recirculation. Goulds’ technical manual identifies submersibles as the more efficient option and recommends considering them where physical dimensions allow. The trade-off is that servicing the submerged unit requires retrieving it. Pump comparison.

Before condemning an existing jet pump

If the pump runs without delivering water, switch it off rather than leaving it to run dry. Lost prime, an air leak, inadequate inlet submergence, a blocked jet or excessive suction loss can resemble pump failure. Frequent cycling can instead involve a leaking check or foot valve, a waterlogged tank or restrictive piping. These are possibilities, not diagnoses from sound alone. Goulds’ troubleshooting guide.

Use the focused guides for a pump that runs but produces no water or safe surface-pump priming. Disconnect power and secure it against reconnection, then relieve pressure before opening the system. Electrical work belongs with a qualified technician; the manufacturer’s safety instructions warn that automatic thermal protection can allow an unexpected restart.

For a replacement quote, supply the installer with the pump model, pumping water level, well yield, casing size, pipe diameters and lengths, available ejector details, desired simultaneous flow and pressure-switch settings. Ask for the expected delivered GPM at your lift and pressure, not merely a horsepower match.