Why Your Pool Pump Is Losing Prime (And How to Fix It)

A swimming pool is a fantastic addition to any home, especially during the hot summer months in Florida. But to keep it sparkling clean and safe for swimming, every part of its circulation system needs to work perfectly. The pool pump is the heart of this system, responsible for pulling water through the skimmer and main drain, pushing it through the filter, and then returning it to the pool. When the pump "loses its prime," this circulation stops, and your pool can quickly turn cloudy and green.

Losing prime means the pump is no longer able to pull water from the pool, and instead is trying to pump air. This can happen for many reasons, ranging from simple fixes to more complex mechanical issues. Understanding the common causes can help you troubleshoot the problem and get your pool back in top shape. This guide will walk you through the most frequent reasons a pool pump loses prime and provide clear, step-by-step instructions on how to fix it.

What Does "Losing Prime" Mean?

Before we get into the solutions, let's clarify what it means for a pump to lose its prime. A pool pump needs a continuous flow of water to function correctly. This is known as its "prime." When the pump housing (the part with the clear lid) is full of water, it can create the suction needed to pull more water from the pool.

If air gets into the system, it breaks this suction, and the pump starts pulling in air instead of water. You might notice the water level in the pump basket chamber is low or that there's no water moving at all. Running a pump without its prime can cause it to overheat and lead to serious damage, making it a problem you need to address quickly.

Common Causes for a Pool Pump Losing Prime

Most priming issues are caused by an air leak on the suction side of the pump—that is, any part of the plumbing before the water enters the pump's impeller. Here are the most common culprits and how to identify them.

1. Low Water Level in the Pool

This is the simplest and most common reason for a pump to lose prime. If the water level in your pool drops below the skimmer opening, the pump will start sucking in air instead of water. This can happen due to evaporation, a leak in the pool liner, or simply from people splashing water out of the pool.

How to Fix It:

Check the water level: The water should be about halfway up the skimmer opening.
Add water: Use a garden hose to fill the pool until the water level is back in the proper range.
Monitor for leaks: If you find yourself constantly refilling the pool, you may have a leak. This requires a more thorough inspection and potentially professional pool repair.

2. A Clogged Skimmer or Pump Basket

Debris like leaves, twigs, and insects can clog the skimmer basket or the pump basket. When these baskets are full, they restrict water flow to the pump. If the blockage is severe enough, the pump will starve for water and start pulling in air, causing it to lose prime.

How to Fix It:

Turn off the pump: Always shut off the power to the pump at the circuit breaker before performing any maintenance.
Clean the skimmer basket: Remove the skimmer lid and lift out the basket. Empty any debris and rinse it with a hose.
Clean the pump basket: Close the skimmer and main drain valves if possible. Then, open the clear lid on the pump, lift out the basket, and clean it thoroughly. Replace the basket and secure the lid.

3. An Air Leak at the Pump Lid O-Ring

The clear lid on your pump has a rubber O-ring that creates an airtight seal. Over time, this O-ring can become dry, cracked, or dirty, allowing small amounts of air to leak into the system. This is one of the most frequent sources of priming problems.

How to Fix It:

Turn off the pump.
Inspect the O-ring: Remove the pump lid and carefully inspect the O-ring for any signs of wear, cracks, or debris.
Clean and lubricate: If the O-ring looks to be in good condition, clean it and the groove it sits in. Apply a silicone-based lubricant specifically designed for pool O-rings before putting it back in place. Do not use petroleum-based lubricants like Vaseline, as they can damage the rubber.
Replace if necessary: If the O-ring is damaged, stretched, or flattened, it needs to be replaced. They are inexpensive and readily available at pool supply stores.

4. A Loose or Cracked Pump Lid

An improperly sealed or damaged pump lid can also be the source of an air leak. If the lid isn't tightened down correctly or has a crack, it won't create the necessary vacuum seal.

How to Fix It:

Check the lid: Ensure the pump lid is seated correctly and tightened securely. Don't overtighten it, as this can cause it to crack.
Inspect for cracks: Carefully check the lid for any hairline cracks, especially around the edges or near the locking mechanism. If you find a crack, the lid will need to be replaced.

5. Leaks in Suction-Side Plumbing

The plumbing that runs from the skimmer and main drain to the pump is known as the "suction side." Any loose fittings, cracks in the pipes, or failing glue joints in this section can introduce air into the system. These leaks are often small and difficult to spot.

How to Fix It:

Inspect the plumbing: With the pump running, carefully examine all the pipes and fittings leading to the pump. You might see small bubbles or hear a faint hissing sound near the leak.
The shaving cream test: To pinpoint a stubborn leak, you can use a fun trick. With the pump on, apply a small amount of shaving cream to any suspected fittings or joints. If there’s an air leak, the pump will suck the shaving cream into the crack, revealing the location.
Repair the leak: Depending on the location and severity, you might be able to fix a small leak with pool-grade PVC cement or epoxy. However, for cracked pipes or significant leaks, professional pool repair in Jacksonville, FL is recommended to ensure a durable and lasting fix.

6. A Stuck Skimmer Weir

The skimmer weir is the small, hinged flap inside the skimmer opening. Its job is to keep debris from floating back into the pool. If this flap gets stuck in the upright position, it can block water from entering the skimmer, causing the pump to suck in air.

How to Fix It:

Check the weir: Simply look into the skimmer and see if the weir is moving freely. If it's stuck, gently push it down to release it.
Inspect for damage: Ensure the tabs that hold the weir in place are not broken. If they are, the weir may need to be replaced.

When to Call a Professional

While many priming issues can be resolved with some basic DIY troubleshooting, some problems require professional expertise. If you've gone through all the steps above and your pump still won't stay primed, it could be a sign of a more serious issue, such as:

A significant underground plumbing leak.
A cracked pump housing or volute.
A faulty valve or seal within the system.

These issues are complex and require specialized equipment to diagnose and fix. Attempting to repair them yourself without the right knowledge could lead to more costly damage. For residents in the North Florida area, finding a reliable service for pool repair in Jacksonville, FL, is the best course of action.

Need Expert Help With Your Pool?

Keeping your pool pump primed is essential for a clean and healthy swimming environment. By regularly checking your pool's water level, cleaning baskets, and inspecting for air leaks, you can prevent most priming problems before they start.

However, if you're struggling to diagnose the issue or the problem requires a more technical solution, don't hesitate to reach out to the experts. If you need professional pool repair in Jacksonville, FL, or the surrounding areas, contact All Phase Pool Remodeling today. Our experienced technicians can quickly identify the source of the problem and provide a reliable solution. Call us for a free estimate and let us help you get back to enjoying your pool.