Pump Losing Pressure

Why Your Pool Pump Suddenly Has Weak Pressure or Reduced Flow

If your pump is losing pressure—weak return jets, low flow, or the pressure gauge dropping—your circulation system isn’t moving water the way it should. This can lead to cloudy water, poor filtration, and heater or salt system shutdowns.

This guide explains the most common causes and what you can check before requesting service.

⭐ 1. Dirty or Clogged Filter (Most Common)

A dirty filter reduces system flow, causing low pressure at the pump and weak return jets.

Signs:

✔ Pressure gauge higher than normal

✔ Weak jet flow

✔ Pump basket full of water but not moving strongly

✔ Salt system showing “Low Flow”

Fix:

• Clean or replace cartridge
• Backwash sand/DE filters
• Confirm pressure returns to normal

A dirty filter is the #1 cause of pressure loss.

⭐ 2. Air Leak on Suction Side

Any air leak before the pump causes the pump to lose prime and lose pressure.

Check for:

✔ Bubbles in pump lid

✔ Bubbles in return jets

✔ Pump basket not staying full

✔ Water surging in and out

Common leak points:

• Pump lid O-ring
• Pump unions
• Skimmer line
• Cracked PVC fittings
• Vacuum line
• Suction valves not fully sealed

Fix:

• Clean/lubricate O-ring
• Tighten unions
• Check for cracks
• Close unused suction ports

⭐ 3. Clogged Pump Basket or Skimmer Basket

If debris blocks flow, you’ll see an immediate pressure drop.

Fix:

• Clean all baskets
• Remove skimmer socks if clogged
• Inspect pump basket for cracks

A cracked pump basket can allow debris into the impeller (see next).

⭐ 4. Impeller Partially Blocked

Small debris—leaves, hair, pebbles—can lodge in the impeller and drastically reduce pressure.

Signs:

✔ Pump gets louder

✔ Weak or uneven pressure

✔ Pump basket doesn’t fully fill

✔ Flow drops over time

Fix:

Pump must be opened and the impeller cleared.

If you suspect this, call for service.

⭐ 5. Pump Speed Too Low (Variable Speed Pumps)

Low RPM settings may not provide enough pressure to operate valves, heaters, or salt systems.

Fix:

• Increase pump speed to 2,500–3,200 RPM
• Temporarily use “Quick Clean” or “Boost” mode
• Check automation schedules

⭐ 6. Water Level Too Low

Low water level causes the skimmer to suck air, lowering pressure.

Fix:

• Raise pool water to mid-skimmer
• Check skimmer weir door movement

⭐ 7. Filter Valve or Bypass Settings Incorrect

On multiport or valve-based systems:

✔ Valve partially closed

✔ Valve in RECIRCULATE or WASTE

✔ Valve diverter worn or misaligned

Fix:

• Make sure valve is fully on FILTER
• Check that dividers are sealing properly

Worn multiport seals will cause circulation issues.

⭐ 8. Leak on Pressure Side (After the Pump)

If water is escaping after the pump, pressure drops.

Possible issues:

• Cracked return pipe
• Loose return union
• Leaking heater bypass
• Filter tank air relief valve leaking
• Increasing amount of air in system

Fix:

Look for visible leaks at the pad.

If underground, professional pressure testing is required.

⭐ 9. Salt System or Heater Restricting Flow

Some equipment will shut down or restrict flow if pressure is too low.

Check:

• Salt system “Low Flow”
• Heater “Low Water Flow”
• Bypass valves incorrectly set

Fix:

Correct the flow issue at the pump/filter first.

⭐ 10. Multiport Valve Glue Joint Failure (Rare)

On older sand/DE filters, the internal spider gasket or glue joints may fail, sending water the wrong direction.

Signs:

• Water returning through waste line
• Constant bubbles or turbulence
• Pressure swings rapidly

This requires repair or multiport replacement.

⭐ When to Contact Professional Pool Company

Call us if:

✔ Pressure drops suddenly without obvious cause

✔ Pump basket won’t stay full

✔ Flow decreases over time

✔ Salt system or heater won’t run due to low flow

✔ You suspect an underground suction leak

✔ Pump is vibrating or noisy

✔ Impeller blockage suspected

We can inspect:

• Suction plumbing
• Pump seals and unions
• Filter internals
• Return plumbing
• Impeller and motor condition

⭐ Summary

A pump losing pressure is usually caused by:

• Dirty filter
• Air leak in suction line
• Clogged baskets
• Impeller blockage
• Low RPM
• Low water level
• Valve misalignment
• Leaks on return side

Most issues can be fixed quickly with basic checks.

⭐ Need Help?

If your pump still loses pressure after these steps, contact Professional Pool Company. We can diagnose suction leaks, plumbing problems, or pump issues and restore proper flow.

Updated on: 29/11/2025