POOL PUMP WON’T PRIME? LOW SUCTION OR VACUUM NOT WORKING?

If you’re dealing with any of these, you’re in the right place:

• Pump basket won’t fill with water (or empties after running)

• You see air bubbles coming from the pool returns

• Water flow is weak / “soft” at the returns

• Vacuum head won’t move or has very weak suction

• Skimmer suction feels weak

• You hear gurgling, surging, or “slurping” sounds

• Filter pressure is abnormal (too high or too low compared to normal)

• Pump runs hot or sounds louder than usual

These symptoms typically point to air entering the suction side, a restriction/clog, or a plumbing leak.

Before assuming the worst, try these quick checks. Many “won’t prime” problems are simple.

1) Check Pool Water Level

If the water is too low, the skimmer can pull air.

Fix: Fill the pool so the water sits roughly mid-skimmer.

2) Empty the Pump Basket and Skimmer Basket

Baskets packed with debris reduce flow and can prevent priming.

Fix: Clean both baskets. If you have two skimmers, check both.

3) Check the Pump Lid O-Ring (Very Common)

A dry, cracked, or dirty lid o-ring lets air in.

What to look for:

• Cracks or flattening
• Dirt/sand on the sealing surface
• Lid not tightened evenly

Fix: Clean the o-ring and seating surface. If you use pool lube, apply a thin coat. Replace if worn.

4) Check for Air Leaks at Unions / Valves

On the suction side, even tiny gaps can pull in air without dripping water.

Look for:

• Drips when the pump turns off
• Wetness around fittings
• Loose unions
• Cracks at valves or fittings

5) Confirm Valves Are Set Correctly

A partially closed valve can choke flow.

Fix: Make sure suction valves are fully open to the skimmer/main drain (based on your setup).

6) Prime the Pump Properly (If Needed)

If the pump lost prime:

• Turn off the pump
• Fill the pump basket with water using a hose
• Reseat the lid firmly
• Turn pump on and watch the basket fill

If it primes but keeps losing prime, that often indicates air intrusion, restriction, or leak.

This is the most important part: is it blocked, or is it leaking?

Signs It’s More Likely a Clogged Line

• Suction is weak and stays weak
• Filter pressure may be higher than normal (if restriction is on the return side) or abnormal overall
• Vacuum won’t move / skimmer doesn’t pull debris
• One skimmer line works, another doesn’t (if you can isolate lines)
• Symptoms started suddenly after a storm, heavy debris, or vacuuming
• Common culprits: leaves, pine needles, toys, plaster chips, collapsed flex pipe (in some installs)

Signs It’s More Likely a Leak (Pulling Air / Losing Prime)

• Pump primes, then loses prime again
• You see consistent air bubbles from returns
• You notice wet spots/soft ground near plumbing runs or equipment
• Water loss in the pool accompanies the issue
• The pump struggles more when certain lines are opened (helps identify which line leaks)

Sometimes it’s both: a partial clog can stress fittings and worsen leaks.

If basic checks don’t solve it, professional diagnosis prevents guesswork and protects your pump.

Here’s what pros typically do (depends on the system and symptoms):

Line Isolation Testing

We isolate skimmer, main drain, and cleaner lines to find which line is causing the problem.

Pressure Testing (Return Lines)

We pressurize lines to see if they hold pressure—this confirms whether there’s a leak underground.

Vacuum Testing (Suction Side)

We test suction lines to detect air leaks and pinpoint where the system is pulling air.

Dye Testing (Skimmer / Fittings)

A safe dye test can confirm leaks around the skimmer throat, fittings, or other suspected areas.

Equipment Pad Inspection Under Load

We inspect valves, unions, pump lid seal, and fittings while running to locate subtle air pulls.

The goal is simple: identify the exact line or component causing the issue, then recommend the right fix.

If you’ve tried the quick checks and your pump still won’t prime (or keeps losing prime), it’s time to get it diagnosed—before you burn out the motor or run the pump dry.

If your pump keeps losing prime, it may be pulling air from a leak or blockage—get it diagnosed before it burns out.