How to Prime a Shallow Well Pump (and What Losing It Means)

Why a jet pump needs priming at all

A shallow well jet pump is a type of centrifugal pump, and centrifugal pumps "have little or no ability to pump air." Before the pump starts, "the pump and suction line needs to have all of the air removed," per Michigan's well construction manual Source 1: Michigan Department of Environment, Great Lakes, and Energy, Water Well Construction Manual1. Without that, the pump spins but never builds the suction it needs to lift water. That water-filled state is what "primed" means.

The same manual explains why a submersible pump skips this entirely: it sits below the water line in the well, so "the pump is always filled with water (primed) and ready to pump" Source 1: Michigan Department of Environment, Great Lakes, and Energy, Water Well Construction Manual1. Texas A&M AgriLife draws the same line plainly: "A submersible pump is a pump that is below ground surface and is submerged in the well water column. A jet pump is typically above ground" Source 3: Texas A&M AgriLife Extension, Shock Chlorination of Wells, ESC-0593. NGWA's national well owner's guide adds the depth context: jet pumps are the pump most often used for shallow wells, "using suction created by a vacuum to lift water out of the well" Source 2: National Ground Water Association, Well Owner's Guide, 2021 edition2.

Put together: if your pump sits above ground and is exposed to air, it can lose its prime. If it sits down in the well, submerged, this is not something that happens to it.

What it means when a pump keeps losing prime

This is the part worth knowing before you assume repriming is just a chore you live with. Michigan's construction rules list "priming not required for ordinary use" as an expectation for a properly built pump installation Source 1: Michigan Department of Environment, Great Lakes, and Energy, Water Well Construction Manual1. In plain terms: a correctly installed, correctly functioning shallow well setup should hold its prime between uses.

So a pump that needs repriming again and again is not behaving normally. It is usually one of two things:

• An air leak in the suction line. Any point where the line can draw in air instead of water will let the pump lose its prime after it shuts off.
• A failed foot valve or check valve. This valve is supposed to hold water in the line when the pump is off. Once it stops sealing, water drains back down and air takes its place.

Neither of those is something repriming fixes. Repriming just resets the symptom until it happens again.

What's reasonably yours, and what needs a pro

With the breaker off, refilling the pump casing with water, per your specific pump's own instructions, and restoring power is a reasonable homeowner check. So is a visual look at any accessible fittings on the suction line for an obvious crack or loose connection.

Two things are not a homeowner job:

• Diagnosing or replacing a foot or check valve. That valve sits at the bottom of the drop pipe, in the well itself. Reaching it means pulling pipe, which is licensed well or pump-contractor work.
• A pump that won't hold prime even right after refilling it. That points at a leak or a valve, not a one-time air pocket, and repeating the refill will not resolve it.

If refilling the pump once solves it and it stays solved, you're done. If it comes back within days, call a well or pump professional rather than repeating the same fix.

Your state's exact rule may differ

Michigan's "priming not required for ordinary use" standard is that state's own construction rule, cited here as an example of how a properly built installation is expected to behave, not a national requirement. Well construction codes vary by state and county. Your local health department or well permitting office has the final word on what applies to your well.

Where this fits

If your pump is cycling strangely rather than losing prime outright, the guide to why well pumps short-cycle covers that separate symptom. The component most often confused with the pump itself is covered in the guide to well pressure tanks. For the maintenance routine a well pump actually needs, see what well pump maintenance actually means. And for the fuller picture of what owning a well involves, see what owning a water well actually means.