Priming a well pump is a critical maintenance step that ensures your water system runs efficiently and avoids permanent damage. If you’ve ever tried to sip through a straw full of air, you’ve experienced the basic problem: pumps are designed to move liquid, not gas.
What is Priming a Well Pump?
Priming of Pump Meaning: Priming a well pump is the process of "bleeding" or removing air from the water pump system.
Priming a pump is simply the process of manually filling the pump casing and the suction pipe with water to push out any trapped air. This creates the necessary vacuum and internal pressure needed for the pump to start "grabbing" water from the ground.
Think of it as "waking up" the system—by adding a little water manually, you give the pump the jumpstart it needs to pull a continuous stream from your well. Without this crucial step, the pump would dry run, which can lead to overheating and permanent damage.
Which Pump Requires Priming?
Not all irrigation well pumps need priming, so it’s important to know which type you have.Generally, any above ground well pump (such as centrifugal pump or jet pump) needs to be primed because air can easily enter the casing.
- Shallow Well Pump (Jet Pumps): These are the most common units that require manual priming a pump. Because they sit above the well and pull water up through a suction pipe, they are highly sensitive to air pockets.
- Centrifugal Pump: Most standard centrifugal pumps are not "self-priming." If the pump housing fills with air instead of water, the impeller will just spin uselessly without creating suction.
- Submersible Well Pump: These are the exception. A submersible well pump is installed deep inside the well, fully submerged in water and not exposed to air. Since it is always underwater, it is "naturally primed" and does not require you to manually add water to start it.
centrifugal pump
How Do You Prime A Shallow Well Pump?
Most centrifugal pumps or jet pump for shallow wells need to be primed before starting because air can get trapped in the suction line, which can prevent proper water flow.Here are the steps to prime a shallow well pump:
1. Turn Off the Power
Always turn off the power to your well water pump before priming. If you’re using a solar well pump, make sure to disconnect the solar panels and turn off the well pump pressure switch to prevent accidental startup.
2. Locate and Open the Prime Plug
As shown in the image, you need to identify the correct access points on your centrifugal pump to ensure all air is removed.
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Find the Priming Port: On this centrifugal pump, the priming port is located at the top of the black pump housing. Use this opening to pour water directly into the pump chamber efficiently with a funnel.
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Open the Air Vent: Locate the small air vent (or bleed screw) on the upper-right side of the pump housing. Loosen it while adding water through the priming port to allow trapped air to escape. Once water flows steadily and all air is released, tighten the vent — the pump is now properly primed.
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Check the Controls: While these ports are open, take a quick look at the pressure switch for well pump located nearby. Ensure the area is clean and dry; this switch is the "brain" of the system that communicates between your shallow well pump with pressure tank and your faucets.
Once the port is open, it’s time to remove the air that is preventing your system from working. As shown in the Properly Primed diagram, the goal is to fill the internal chamber of the centrifugal pump completely so that the pump impeller is entirely submerged in water.
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Filling the Casing: Slowly pour clean water into the priming port. As the water enters, it will travel down through the pump housing and into the suction pipe leading to your well.
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Creating the Vacuum: For a shallow well pump with pressure tank, this liquid acts as a seal. Without it, as seen in the Not Properly Primed image, air pockets will remain at the top of the housing, causing the pump to lose its "grip" and fail to draw water.
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The Role of the Foot Valve: You must continue pouring until the water stays level at the very top of the priming hole. If the water level continuously drops, it likely means your foot valve at the bottom of the well is leaking. This valve must hold the water in the pipe like a finger on the top of a straw; if it fails, you won't be able to prime your shallow well water pump.
Continue this process until all air bubbles stop rising. Ensuring the housing is 100% full is the secret to getting a solar well pump or electric pump to successfully pull water into your pressure tanks for wells.
4. Seal and Start the Water Well Pump
Once the housing is completely full and no air bubbles remain, it is time to close the system and restore power. Follow these steps to ensure a successful start:
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Secure the Seal: Wrap the threads of your priming plug with plumber’s tape to create an airtight seal, then screw it back into the port tightly. Even a tiny air leak at this connection can cause a shallow well water pump to lose its prime immediately.
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Restore Power: Reconnect your solar well pump to its controller or flip the power switch back on. You should hear the centrifugal pump motor engage; a deep, steady hum indicates it is successfully moving water rather than air.
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Monitor Pressure: As the pump runs, it will begin to draw water from the well to fill your pressure tanks for wells. Keep an eye on the pressure switch for well pump to ensure it automatically shuts the motor off once the system reaches its target pressure.
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Verify the Valve: A functional well pump check valve is essential for a shallow well pump with pressure tank. This valve (along with the foot valve) acts as a one-way gate that prevents water from flowing backward into the well. If the pump starts but the pressure drops the moment it stops, your well pump check valve may be stuck or leaking, requiring maintenance to keep the system ready for the next use.
With all steps properly completed, you can now safely start your well pump and enjoy a steady water supply.
