How to Prime a Jet Pump

Jet Pumps

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

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

If your pump has lost prime, you may notice these symptoms:

• 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

These symptoms usually indicate the pump housing or suction line contains air instead of water.

Tools Needed to Prime a Jet Pump

Before starting, gather these tools:

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

Having the right tools ready will make the process faster and easier.

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

Follow these steps carefully to restore your pump's prime.

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
• a hose
• a hand primer pump

Continue filling until the pump housing and suction pipe are completely full.

This water allows the pump to generate suction when it starts.

Step 5: Replace the Priming Plug

Once the pump is full:

• reinstall the priming plug
• tighten it securely
• 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
• shut off automatically when the pressure switch reaches the set pressure

If the pump does not prime immediately, repeat the process.

Why Jet Pumps Lose Prime

Several issues can cause a jet pump to 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
• 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.

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.

This prevents 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

Professional pump technicians often recommend:

• Filling the suction pipe completely
• Sealing all threaded connections
• Checking the foot valve for leaks
• Installing a ball valve on the discharge side
• Slightly opening the valve during startup

These steps help the pump build suction more quickly.

When to Call a Pump Professional

If your pump continues losing prime, the problem may involve:

• a failed foot valve
• suction line leaks
• worn pump seals
• a dropping well water level
• internal pump damage

A pump technician can diagnose the issue and restore proper system operation.

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:

• bad foot valve
• suction pipe air leaks
• low well water level
• 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.

Final Thoughts

Priming a jet pump is an essential part of maintaining a reliable well water system.

By filling the pump housing with water and ensuring there are no air leaks in the suction line, you can restore water flow and prevent costly pump damage.

Regular inspection of valves, pipes, and fittings can also help prevent future priming issues.

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.

Have a question about priming a jet pump? You can live chat with us at www.rcworst.com, call 855.329.4519, or email Customer.Service@RCWorst.com to reach an industry expert

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