Air Leak Diagnosis

How to Identify and Fix Air Leaks in Your Pool System

Air leaks cause a wide range of pool equipment problems, including:

• Pump losing prime
• Low flow / Low Flow alerts
• Heater shutting off
• Salt system not producing
• Bubbles from the return jets
• Noisy pump or cavitation

Most air leaks occur on the suction side of the system (before the pump), where the pump pulls water under vacuum. Even the smallest leak can suck in air and disrupt system performance.

This guide explains how to diagnose the source of an air leak and what to check before contacting us.

⭐ 1. Pump Lid O-Ring — #1 Cause of Air Leaks

The pump lid must form an air-tight seal.

If the O-ring is dry, cracked, flattened, or dirty, air will enter the pump instantly.

Signs:

✔ Bubbles under pump lid

✔ Pump takes long time to prime

✔ Return jets produce bubbles

✔ O-ring looks dry or misshapen

Fix:

• Remove lid
• Clean O-ring and lid groove
• Apply silicone lubricant
• Reseat O-ring properly
• Tighten lid firmly

If O-ring is worn → replace it.

⭐ 2. Pump Inlet Union or Suction Fittings Loose

Loose fittings allow air to enter without leaking water.

Check:

✔ Union hand-tightened?

✔ O-ring inside union in good condition?

✔ Cracks around threaded fittings?

Fix:

• Hand-tighten unions (do NOT over-tighten)
• Replace cracked unions
• Replace worn O-rings

⭐ 3. Water Level Too Low

If water is below mid-skimmer, the skimmer will suck air.

Fix:

• Raise water level to halfway up the skimmer opening
• Verify the skimmer weir door moves freely

Low water level is one of the most common air leak sources.

⭐ 4. Skimmer Issues

Air enters when:

✔ Skimmer weir door stuck

✔ Basket cracked

✔ Debris preventing consistent water draw

Fix:

• Clean basket
• Straighten or free the weir door
• Replace cracked baskets

⭐ 5. Vacuum Hose or Suction Cleaner Leak

Vacuum hoses often develop pinholes or loose connections.

Signs:

✔ Bubbles only when vacuum is connected

✔ Pump loses prime intermittently

✔ Hose floats or sucks air

Fix:

• Replace old/rigid hose sections
• Make sure all hose joints are submerged
• Check O-rings at connection points

⭐ 6. Suction Valves Not Fully Sealed

If a valve is partially closed or worn, air can enter.

Check:

✔ Valve handle alignment

✔ O-rings inside valve

✔ Cracks in valve housing

Fix:

• Open valves fully
• Replace internal valve O-rings
• Replace defective valves

⭐ 7. Pump Basket Cracked

Even a tiny crack allows air to bypass the basket and reach the pump.

Fix:

Replace the pump basket immediately.

⭐ 8. Suction-Side Plumbing Crack

Cracks in PVC or underground suction lines allow air in when pump is on.

Signs:

✔ Large amounts of air

✔ Pump won’t stay primed

✔ Air returns after bleeding system

✔ Worse when suction valves adjusted

Fix:

Professional pressure testing required.

Underground suction leaks typically need repair or re-route.

⭐ 9. Filter Air Relief Valve Leaking

If air relief valve O-ring is worn, air may re-enter the system after filtering.

Fix:

• Tighten air relief knob
• Replace O-ring if leaking

⭐ 10. Salt Cell Union Leak

Salt systems have unions that can allow air to enter.

Check:

✔ Unions hand-tight?

✔ O-rings in good condition?

✔ Salt cell installed in correct direction?

⭐ 11. Pump Seal Failure (Less Common)

If the mechanical seal is damaged, air may enter the pump—often accompanied by water leaking out.

Signs:

✔ Water dripping under motor

✔ Rust at seal plate

✔ Chirping/grinding noises

Requires professional repair.

⭐ 12. Diagnosing Air Leaks Step-by-Step

Follow this exact sequence:

Step 1 — Check pool water level

Mid-skimmer or slightly higher.

Step 2 — Inspect pump lid O-ring

Clean, lubricate, and reseat.

Step 3 — Tighten pump inlet unions

Ensure fittings are snug and not cracked.

Step 4 — Clean all baskets

Skimmer, pump basket, and leaf traps.

Step 5 — Check vacuum hoses

Look for pinholes and loose connections.

Step 6 — Inspect suction valves

Verify full alignment and check for wear.

Step 7 — Observe pump while running

Look for air patterns, surging, or gurgling.

If the pump still draws air → likely an underground suction leak or internal pump issue.

⭐ When to Contact Professional Pool Company

Call us if:

✔ Pump cannot maintain prime

✔ Large or constant air bubbles

✔ Pump surges or gurgles

✔ Air returns immediately after bleeding

✔ You suspect an underground leak

✔ Pump seal or impeller appears damaged

We can pressure test suction lines, inspect fittings, and identify exact leak points.

⭐ Summary

Air leaks are most commonly caused by:

• Bad pump lid O-ring
• Loose pump unions
• Low water level
• Skimmer or vacuum leaks
• Suction valve issues
• Cracked pump basket
• Underground suction-side plumbing leak

Most leaks can be fixed quickly with simple checks.

⭐ Need Help?

If your system has persistent air leaks, contact Professional Pool Company. We can diagnose suction leaks, pump issues, and plumbing problems to restore full system performance.

Updated on: 29/11/2025