Why Is My Pump Losing Pressure? Common Causes and Fixes

Quick Answer

A pump that loses pressure is commonly caused by leaks, a failed pressure vessel, incorrect air charge, faulty pressure switch, blocked filters, failed non-return valve, air in the system, worn pump parts or incorrect pump sizing.

If pressure drops quickly, the pump cycles frequently, or the system cannot meet demand, the fault should be checked before it causes further damage.

What Does Pump Pressure Loss Mean?

Pump pressure loss means the system cannot maintain the pressure it is designed to provide.

This may show as weak flow, fluctuating pressure, the pump restarting too often, taps or outlets losing power, alarms, or the system working harder than normal.

If the pump is also starting and stopping repeatedly, read our pump short cycling guide.

1. Leaks in the Pipework or System

Leaks are one of the most common causes of pressure loss. Even a small leak can make the pump restart frequently or struggle to maintain pressure.

Leaks may occur in pipework, valves, fittings, tanks, pressure vessels, seals or downstream equipment.

Sometimes the leak is visible, but hidden leaks can also cause pressure to drop when no water is being used.

How to Fix Leak-Related Pressure Loss

Check for visible damp patches, dripping fittings, leaking valves and pressure drops when outlets are closed.

If there is no obvious leak, the system may need professional pressure testing or isolation checks to find where pressure is being lost.

2. Failed Pressure Vessel

A pressure vessel helps stabilise pressure and reduce how often the pump starts. If the vessel has failed or lost its air charge, pressure may drop quickly.

A failed pressure vessel can also make the pump cycle on and off repeatedly, which increases wear on the motor.

Signs include pressure rising and falling quickly, the pump starting frequently, weak flow and inconsistent water pressure.

How to Fix a Pressure Vessel Fault

The pressure vessel should be checked for correct air charge, waterlogging, bladder failure and general condition.

If the bladder has failed or the vessel is damaged, replacement is usually required.

3. Faulty Pressure Switch

The pressure switch controls when the pump starts and stops. If it is set incorrectly or failing, the pump may not maintain pressure properly.

A faulty pressure switch may cause delayed starting, early stopping, short cycling or inconsistent pressure.

Pressure switch issues can look similar to pressure vessel faults, so both should be checked together.

How to Fix Pressure Switch Issues

The switch settings should be checked against the system requirements. If the switch is worn, blocked or unreliable, it may need replacement.

Do not keep adjusting pressure settings without checking the vessel, valves and wider system, as this can hide the real fault.

4. Failed Non-Return Valve

A non-return valve, also known as a check valve, prevents water flowing back through the system after the pump stops.

If the valve fails, pressure can drain away, causing the pump to restart or pressure to fall when it should remain stable.

This is a common reason for pressure dropping shortly after the pump switches off.

How to Fix a Valve Fault

The valve should be checked for debris, sticking, wear or failure. Cleaning may help if debris is the issue, but a worn valve usually needs replacement.

If valves keep failing, filters and system cleanliness should also be reviewed.

5. Blocked Filters or Restricted Flow

Blocked filters, strainers or inlets can restrict flow and make pressure drop at outlets.

This can happen where sediment, scale, debris or sludge builds up in the system.

Restricted flow may also make the pump louder, less efficient or more likely to overheat.

How to Fix Restricted Flow

Filters and strainers should be inspected, cleaned or replaced. Pipework, valves and inlets may also need checking.

Routine servicing helps prevent restriction-related faults. See our pump maintenance checklist for recommended checks.

6. Air in the System

Air trapped in the pipework or pump can cause pressure fluctuation, spluttering outlets, inconsistent flow and difficulty maintaining pressure.

Air can enter through leaks, poor priming, low supply levels or suction-side faults.

If the pump is running but not moving water properly, see our pump running but not pumping water guide.

How to Fix Air Problems

The system may need bleeding, re-priming or checking for suction-side leaks.

If air returns after bleeding, the source of the air ingress needs to be identified and repaired.

7. Worn Pump Components

Over time, pump components such as impellers, seals, bearings and internal wear parts can reduce performance.

The pump may still run, but it may not build or maintain the pressure it used to.

Signs include declining performance, noise, vibration, overheating or recurring faults.

Repair or Replace?

If the pressure loss is caused by a serviceable component, repair may be the best option.

If the pump is older, inefficient, repeatedly failing or no longer suitable for demand, replacement may offer better value.

Read our pump repair vs replacement guide for help comparing both options.

8. Incorrect Pump Sizing

A pump that is too small may struggle to maintain pressure when demand increases. A pump that is too large may cycle frequently and cause pressure instability.

Sizing issues are common when system demand has changed, pipework has been altered or the original pump was not specified correctly.

If the system has never performed properly, the pump duty and installation should be reviewed.

When Should You Be Concerned?

Pressure loss should be treated as urgent if the pump cannot meet demand, pressure drops suddenly, the pump runs constantly, alarms appear, or there is a risk of flooding, water supply failure or business interruption.

You should also act quickly if there are leaks, overheating, unusual noise or repeated electrical trips.

How to Prevent Pressure Loss

Regular servicing helps identify pressure vessel faults, valve issues, leaks, blocked filters and worn pump components before they become serious.

Maintenance should include checking pressure settings, vessel condition, filters, valves, pipework, controls and general pump performance.

For wider reliability advice, read our guide to why pump systems fail.

Professional Pump Pressure Diagnosis

Pressure loss can have several possible causes, so proper diagnosis is important before replacing parts.

At Alton Facility Services, we inspect, service and repair pump systems for domestic, commercial, drainage and wastewater applications across Hampshire, Surrey and the surrounding areas.

Need help with a pump losing pressure? Contact our team or call 01420 561661 to arrange an inspection.

How AFS would diagnose the pump fault

Pump faults are often caused by more than the pump itself. AFS would normally check the pump, floats, valves, non-return valves, control panel, electrical supply, alarm circuit, discharge pipework, chamber condition and signs of blockage or overload.

Where the system is critical, the safest route may be urgent pump station repair, planned pump servicing, or a properly specified pump installation rather than repeated temporary resets.

Repair, servicing or replacement?

A pump can often be repaired if the issue is a blockage, float fault, worn component or control issue. Replacement is more likely where the pump is badly worn, incorrectly sized, unreliable, obsolete or repeatedly failing.

For sewage and wastewater systems, AFS can also review the wider chamber, rising main and control arrangement. That matters because a new pump will not solve a poor installation, undersized rising main or failed control panel.

Useful related AFS services

Useful next pages include pump servicing, pump installation, pump station repair services, package pump stations and sewage pumps.

Need practical help with this?

For pump faults, pump station alarms, servicing, repair and replacement, AFS can check the wider system and advise whether the issue is mechanical, electrical, hydraulic or installation-related. You can call 01420 561661 or send details through the contact form.