How to Prime a Jet Pump

Jet pumps are commonly used in private well systems to move water from shallow wells or storage tanks into homes and irrigation systems.

Before a jet pump can operate properly, it must be primed with water. Priming fills the pump housing and suction pipe so the pump can create the vacuum needed to draw water from the well.

If your jet pump loses prime, the pump may continue running but no water will come out of your faucets.

This guide explains:

• What priming a pump means
• How to prime a jet pump step-by-step
• Why pumps lose prime
• How to troubleshoot priming problems
• Tips to get your well pump running again quickly

Shop Jet Pumps

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• Myers MPNC Shallow Well Jet Pump 0.5 HP — reliable workhorse for residential shallow wells
• Shakti SPS5 0.5 HP Shallow Well Jet Pump — compact and efficient for light-duty applications
• Shakti SPS10 1.0 HP Shallow Well Jet Pump — more power for higher demand systems

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What Does Priming a Pump Mean?

Priming a pump means filling the pump casing and suction line with water before starting the pump.

Jet pumps depend on water inside the pump housing to create suction pressure. Without water in the system:

• The pump cannot pull water from the well
• The pump will run dry
• Internal components may overheat and become damaged

This is why running a pump without priming can cause serious pump failure.

Signs Your Jet Pump Has Lost Prime

• Pump runs but no water flows
• Air sputtering from faucets
• Low or inconsistent water pressure
• Pump runs continuously without shutting off
• Pressure gauge not building pressure

Tools Needed to Prime a Jet Pump

• Bucket of clean water
• Garden hose
• Hand primer pump (optional)
• Wrench or pliers
• Screwdriver
• Pipe thread sealant or Teflon tape

Step-by-Step: How to Prime a Jet Pump

Step 1: Turn Off Power to the Pump

Before working on the pump, turn off the circuit breaker that supplies power to the well pump. This prevents accidental pump startup while priming.

Step 2: Locate the Priming Plug

Most jet pumps have a priming plug on the top of the pump housing. Some systems include a vertical tee fitting with a plug or valve used specifically for priming.

Step 3: Remove the Priming Plug

Using a wrench or screwdriver, carefully remove the priming plug. Avoid damaging the threads since a poor seal could allow air into the pump.

Step 4: Fill the Pump With Water

Pour clean water into the priming port using a bucket, hose, or hand primer pump. Continue filling until the pump housing and suction pipe are completely full.

Step 5: Replace the Priming Plug

Reinstall the priming plug, tighten it securely, and apply Teflon tape if needed. A tight seal prevents air leaks.

Step 6: Turn the Pump Back On

Restore power at the breaker panel. If the pump primes successfully, it should begin pumping water, build system pressure, and shut off automatically when the pressure switch reaches the set pressure.

Why Jet Pumps Lose Prime

Air Leaks in the Suction Line

Even a tiny air leak can break the suction needed to draw water from the well. Check pipe fittings, unions, and threaded connections.

Bad Foot Valve

A foot valve located at the bottom of the well pipe prevents water from draining back into the well. If the valve fails, water drains out of the suction line and the pump loses prime. We carry quality replacement foot valves:

• Flomatic Foot Valve 3"
• Flomatic Foot Valve 4"

Low Well Water Level

If the well water level drops below the intake pipe, the pump cannot draw water. This can happen during heavy water use or drought conditions.

Loose or Cracked Pipes

Cracked suction pipes or loose fittings allow air to enter the system, preventing the pump from maintaining suction.

Worn Pump Seals

Older pumps may develop worn seals that allow air into the pump housing.

Tips to Prime a Jet Pump Faster

• Fill the suction pipe completely
• Seal all threaded connections with Teflon tape
• Check the foot valve for leaks
• Install a ball valve on the discharge side
• Slightly open the valve during startup

Frequently Asked Questions

How long does it take to prime a jet pump?

Most jet pumps prime within 30 seconds to a few minutes after being filled with water.

Why does my jet pump keep losing prime?

The most common causes include a bad foot valve, suction pipe air leaks, low well water level, or loose pipe connections.

Can a jet pump prime itself?

Some jet pumps are self-priming, but they still require the pump housing to be filled with water initially.

Can running a pump without priming damage it?

Yes. Running a dry pump can cause overheating, seal damage, and impeller wear.

Related Guides

• 📖 30/50 or 40/60 PSI: What Pressure to Set Your System To
• 📖 How to Adjust a Pressure Switch
• 📖 Troubleshooting a Jet Pump — Low Pressure or Flow

Need Expert Help?

If your pump continues losing prime or you're not sure what's causing the issue, our water system experts are here to help.

Get Expert Help →

You can also live chat with us at www.rcworst.com, call 855.329.4519, or email Customer.Service@RCWorst.com.

Pro tip: To increase your likelihood of success, install a ball valve on the discharge side, crack it open slightly at startup, and slowly open it once you hear the water fill the pipe.