What priming means and why your pump needs it
Priming means filling the pump chamber and intake line with water so the pump can create suction and move water from your well or source into your home. Without priming, a pump full of air cannot pull water up—it will just spin and push air around. If you have drained your system for repairs, winterized it, or installed a new pump, you will need to prime before water flows again.
A pressure tank does not prime itself. The tank stores pressurized water and helps maintain steady pressure, but it cannot create the initial suction the pump needs to draw water from below ground. You must fill the pump housing with water by hand or through a fill valve before the pump can work.
Key Takeaways
- Priming means filling the pump chamber with water so it can create suction and pull water from your well or source.
- Locate the priming plug or fill valve on top of the pump housing—this is where you pour water in or connect a hose.
- Fill the pump chamber slowly until water comes out of the vent or until the chamber is completely full, then close the plug.
- Turn on the pump and listen for the sound of water moving; it may take 30 seconds to several minutes for water to reach your tank and faucets.
- If the pump runs but no water appears after 5 minutes, the intake line may have an air leak and will need to be checked for cracks or loose fittings.
Locate the priming plug or fill valve on your pump
The priming plug is a small bolt or valve on the top or side of the pump housing, usually about the size of a quarter or half-dollar. Look at the pump body itself—not the pressure tank. On most residential jet pumps and submersible pump housings, the plug sits on the highest point of the pump casing. If you cannot find it, check your pump manual or look for a small hole with a bolt or a valve handle.
Some newer pumps have a fill valve instead of a plug—it looks like a small faucet or ball valve and may have a hose connection. If your pump has a fill valve, you can attach a garden hose to it and run water in from a nearby faucet. If it has only a plug, you will pour water in by hand using a bucket or pitcher.
Before you open the plug, turn off the pump at the breaker or switch. Do not prime a running pump—you risk damaging the impeller or creating an unsafe pressure surge.
Fill the pump chamber slowly and completely
Use a bucket or pitcher to pour water into the priming plug opening. Pour slowly so the water has time to fill the chamber and displace the air inside. You will see air bubbles escape from the opening as the water level rises. Keep pouring until water flows steadily out of the opening without bubbles, or until water reaches the top of the chamber and will not take any more.
If your pump has a vent screw or air release valve (a small bolt on the side or top), open that first before you prime. This lets air escape more easily as you fill. Once water comes out of the vent, close it, then continue filling the main chamber until it is completely full.
Do not rush this step. If you pour too fast, air pockets can form inside the pump and prevent proper priming. A typical pump chamber takes 2 to 5 minutes to fill by hand. Once the chamber is full and no more air bubbles appear, close the priming plug firmly—hand-tight is usually enough; do not over-tighten.
Turn on the pump and listen for water movement
Switch the pump on at the breaker or control switch. You should hear the motor start and, within a few seconds, the sound of water moving through the pipes. The pump may make a gurgling or sputtering noise for the first 10 to 30 seconds as it pushes out remaining air pockets. This is normal.
Water should begin flowing from your faucets or into the pressure tank within 30 seconds to 2 minutes. If you have a pressure gauge on the tank, watch it—the needle should start to rise as water enters and the pump builds pressure. Once the pressure reaches your pump's cut-off point (usually 40 to 60 pounds per square inch), the pump will shut off automatically.
If the pump runs but you hear only air hissing and no water sound after 30 seconds, stop the pump and wait 5 minutes. Then repeat the priming process. Sometimes a second priming is needed if air pockets remain.
What to do if the pump runs but no water appears
If you have primed the pump twice and the motor runs but no water comes out of your faucets or into the tank after 5 minutes, the problem is usually an air leak in the intake line. The intake line is the pipe that runs from your well or water source down into the pump. If this line has a crack, loose fitting, or puncture, it will suck in air instead of water, and the pump cannot maintain suction.
Check all visible fittings and connections on the intake line for water dripping or spraying. Tighten any loose fittings by hand or with a wrench. If you find a crack in the pipe itself, that section will need to be replaced. If the intake line runs underground or is not visible, you may need to call a well service technician to locate and repair the leak.
Another less common cause is a clogged intake screen or check valve. If your pump has an intake screen (a small strainer at the bottom of the intake line), sediment or debris may be blocking it. A check valve (a one-way valve in the intake line) can also stick closed. Both of these require opening the intake line to clean or replace the part.
Priming after winterization or a long shutdown
If you drained your system for winter or the pump has sat unused for weeks, priming may take longer than usual. Sediment or rust may have settled in the pump chamber or intake line. Prime as normal, but be patient—it may take 3 to 5 minutes for water to reach your faucets the first time.
Once water starts flowing, let the pump run for 5 to 10 minutes without stopping. This flushes out any sediment or air pockets still in the lines. You may notice the water looks cloudy or discolored at first—this is normal and will clear as the system runs. If the water remains discolored after 10 minutes of running, turn off the pump and let it sit for an hour, then prime and run again.
If you have a sediment filter or whole-house filter on your system, check it after priming. A long shutdown can allow sediment to accumulate, and the filter may need cleaning or replacement before water pressure returns to normal.
Common mistakes that prevent successful priming
The most common mistake is not filling the pump chamber completely. Many people pour water in until they see water come out of the vent, then stop. But the main chamber may still have air pockets. Always fill until water reaches the very top of the opening and will not take any more water.
Another mistake is priming a pump that is already running. Always turn off the pump before you open the priming plug. Priming a running pump can damage the impeller or create a sudden pressure surge that damages pipes or fittings.
A third mistake is not checking the intake line for air leaks. If the pump runs but no water appears, many people assume the pump is broken and call for service. In most cases, a loose fitting on the intake line is the real problem and can be tightened in minutes.
Frequently Asked Questions
How long should I wait after priming before I turn on the pump?
You can turn on the pump when ready after priming and closing the priming plug. There is no waiting period. The pump should start pulling water right away. If you have just finished filling the chamber, the water is already in place and ready to create suction.
Do I need to prime the pressure tank separately?
No. The pressure tank does not need priming. It fills automatically once the pump starts running and water enters the system. The tank is straightforward a storage vessel and does not create suction. Prime only the pump itself.
What if water leaks out of the priming plug when I close it?
A small drip is normal if you have just finished filling. Tighten the plug by hand—do not use a wrench, as this can crack the fitting. If water continues to leak after hand-tightening, the plug may have a damaged seal. Turn off the pump, remove the plug, wrap the threads with plumber's tape, and reinstall it.
Can I use any water to prime the pump, or does it have to be from a specific source?
You can use water from any clean source—a hose, a bucket, or a nearby faucet. The water does not have to be from your well. You are straightforward filling the chamber to create suction; once the pump starts, it will draw water from your actual source.
Why does the pump make noise after I prime it?
Gurgling, sputtering, or hissing sounds in the first 30 seconds are normal and mean air is still leaving the system. These sounds should stop once the pump has run for a minute or two. If the noise continues after 5 minutes, turn off the pump and prime again.