How to Prime a Pump for Well Water

To prime a well-water pump, switch off and isolate its power, relieve system pressure, remove the designated priming plug, and fill the pump casing—and, where the manual directs, the suction piping—with clean water. Refit the plug before restoring power. If the pump does not begin delivering water within the time allowed by its manual, switch it off and refill rather than letting it run dry.

This procedure applies to above-ground jet pumps, including many shallow-well and deep-well jet systems. It does not normally apply to a submersible pump down inside the well.

First identify the pump

What you have	Does it need manual priming?
Above-ground shallow-well jet pump with one suction pipe	Usually, after installation, draining, repair or loss of prime
Above-ground deep-well jet pump with two pipes into the well	Yes, but filling and startup instructions can differ by model
Submersible pump below the water level	Not by pouring water into an above-ground priming port

A submersible well pump is installed below the drawdown water level, and its discharge check valve keeps water in the drop pipe while the pump is stopped. If that system has no water, troubleshoot the power, controls, water level, check valves and piping rather than looking for a priming plug. Zoeller’s submersible-pump manual specifies that the complete pump and motor should remain submerged and explains that the discharge-head check valve maintains water in the pipe when the pump is off (Zoeller).

If the pump type is uncertain, follow the pipes. A surface pump with one pipe running toward the well is commonly a shallow-well arrangement; two well pipes commonly indicate a deep-well jet assembly. Goulds Water Technology makes this distinction in its jet-pump selection guide (Xylem).

Before opening the priming port

Find the pump’s model number and its installation manual. The approved fill point, venting method and maximum startup interval are model-specific.

Then:

1. Disconnect and lock out electrical power. A pressure switch can start the pump automatically. Goulds instructs users to disconnect and lock out power before installation or service because thermal overload protection can also permit an unexpected restart (Xylem).
2. Relieve water pressure. Open a faucet or drain and confirm that the pressure gauge falls before loosening a plug.
3. Let a hot motor or pump cool. Do not handle hot equipment or open a pressurized casing.
4. Inspect before filling. Look for a cracked casing, damaged cord, wet electrical components or burned wiring. Stop if any are present.
5. Gather clean water, a clean funnel if needed, and the correct wrench. Do not substitute a random casing bolt for the manufacturer’s designated priming plug.

Priming an above-ground jet pump

1. Keep the power off. Confirm that the breaker or disconnect cannot be switched on while the priming port is open.
2. Open the intended air-release path. Depending on the manual, this may mean opening a downstream faucet while filling. Do not alter pressure-switch settings or remove its cover.
3. Remove the priming plug. It is usually on top of the pump casing or on a tee at the discharge, but use the model diagram rather than location alone.
4. Fill slowly with water. Fill the pump casing completely. If the manufacturer provides a suction-line priming tee, fill through that point as directed. Pentair’s shallow-well instructions call for filling the pump and all piping between the pump and well; Goulds’ E-Z Prime instructions say to fill the casing until water exits the priming hole freely without air bubbles (Pentair, Xylem).
5. Watch the water level. A brief drop as trapped air moves is possible. A level that keeps falling can indicate that the suction-side check or foot valve is not holding, or that suction piping is leaking.
6. Refit the priming plug as the manual specifies. Pentair requires replacement of all fill plugs before startup. Do not leave a plug loose merely because another pump’s instructions use that method.
7. Restore power and start the pump. Keep a discharge path available if the manual requires it; never run against a closed discharge.
8. Stop promptly if water does not arrive. Pentair’s cited models specify stopping after two or three minutes without water, then refilling the pump and piping. Treat that as a model-specific limit, not permission to run every pump for three minutes. The same manual warns that dry running can overheat the pump, damage its seal and create a burn hazard (Pentair).
9. Verify operation. Once flow is free of large air bursts, close the opened faucet gradually. Confirm that pressure rises to cut-out, the pump stops, and it restarts normally when water use lowers pressure.

If it will not prime—or will not stay primed

Repeatedly adding water is a test, not a repair. Goulds states the useful principle directly: pumps do not hold prime; the piping system and check valves do (Xylem).

Use what happens during filling and startup to narrow the fault:

• Water disappears down the priming port while power is off: suspect a nonholding foot valve or check valve, or a suction-line leak.
• The casing stays full but the pump produces no water: check for a closed valve, an air leak at a fitting or union, trapped air at a high point, an obstructed jet or a water level beyond the system’s workable suction lift.
• The pump primes but loses prime after sitting: focus on check-valve sealing and suction-pipe leaks.
• Flow arrives but pressure never reaches cut-out: switch the pump off. Possible causes extend beyond priming and include a plumbing leak, low well yield, blocked jet, worn pump or unsuitable pump setup.
• The motor hums, trips the breaker, leaks at the shaft or becomes very hot: stop rather than repeating startup attempts.

Suction leaks can admit air without showing an obvious water leak. Pentair warns that suction joints must be both airtight and watertight; if the suction pipe draws air, the pump cannot pull water from the well (Pentair). High spots in the suction line can also trap air and make priming difficult.

For a broader decision path after an unsuccessful attempt, see how priming changes by pump type and setup. If the pump runs but the house still has no water, work through the separate jet-versus-submersible checks rather than continuing to run it.

Stop and call a qualified well-pump technician or electrician when the system has damaged wiring, wet electrical equipment, repeated breaker trips, inaccessible buried components, a suspected failed down-well valve, or no reliable way to isolate power. Priming can remove air from a sound jet-pump system; it cannot correct an electrical fault, a dry well or a leaking suction assembly.