If you rely on a water pump for your home’s water supply, you may notice it turning on and off far more often than expected. This behaviour, commonly referred to as pump cycling or short cycling, is more than just an annoyance. In many cases, it’s a sign that something in the system isn’t working as it should.
Understanding why a water pump keeps cycling can help prevent unnecessary wear, reduce energy use, and avoid more serious pump or plumbing failures. This article explains what pump cycling is, why it happens, and when it’s time to investigate further.
What Does “Pump Cycling” Mean?
A water pump is designed to turn on when water pressure drops and turn off once pressure is restored. In a healthy system, this happens gradually and predictably. Cycling becomes a problem when the pump switches on and off repeatedly within a short period, sometimes every few seconds or minutes.
This constant stopping and starting places strain on the pump motor, pressure switch, and electrical components. Over time, it can significantly shorten the lifespan of the pump and increase the risk of failure.
Pressure Tank Problems Are the Most Common Cause
One of the most frequent reasons a water pump keeps cycling is an issue with the pressure tank. The pressure tank stores water under pressure and acts as a buffer so the pump doesn’t need to run every time a tap is opened.
If the tank’s internal bladder is damaged or has lost air pressure, the tank can no longer hold enough pressurised water. As a result, even a small demand for water causes an immediate pressure drop, triggering the pump to turn on. Once pressure rises slightly, the pump shuts off again, creating a rapid cycle.
In many cases, this issue develops gradually, which is why cycling often worsens over time rather than appearing suddenly.
Incorrect Pressure Tank Air Charge
Even if the pressure tank itself is intact, incorrect air pressure inside the tank can cause cycling. Pressure tanks rely on a precise balance between air pressure and water pressure. If the air charge is too low, the tank fills with water too quickly and provides little buffering. If it’s too high, the system may struggle to maintain stable pressure.
Air pressure issues can occur naturally over time or after maintenance if the tank wasn’t re-pressurised correctly. This is a common cause of cycling in systems that otherwise appear to be in good condition.
Leaks in the Plumbing System
A water pump will continue to cycle if water pressure cannot stabilise. One reason this happens is a leak somewhere in the system. Even a small, slow leak can cause pressure to drop enough for the pump to restart repeatedly.
These leaks are not always obvious. They can occur in underground pipework, irrigation systems, toilets, or fittings that are rarely used. Because the pump is responding to pressure loss rather than visible water, cycling may be the first noticeable symptom.
Faulty Pressure Switches
The pressure switch controls when the pump turns on and off based on system pressure. If this switch becomes worn, blocked, or incorrectly calibrated, it may trigger the pump too frequently or at the wrong pressure levels.
A failing pressure switch can cause the pump to:
- Turn on earlier than it should
- Shut off too quickly
- React inconsistently to pressure changes
Because the pressure switch is a relatively small component, it’s sometimes overlooked, but it plays a critical role in stable pump operation.
Check Valves Not Holding Pressure
Check valves are designed to prevent water from flowing backward once pressure has been built up. If a check valve fails or does not seal properly, pressure can bleed back through the system after the pump shuts off.
When this happens, the pump senses the pressure drop and restarts, even though no water is being used. This type of cycling often occurs when no taps are open, which can make it confusing to diagnose without proper testing.
Demand That Exceeds System Design
In some homes, cycling isn’t caused by a fault but by system limitations. Adding extra bathrooms, irrigation systems, or high-demand appliances can place more strain on an existing pump setup.
If the pressure tank is undersized or the pump is operating near its capacity, the system may struggle to maintain steady pressure during use. This can result in frequent cycling, particularly when multiple outlets are running at once.
Why Short Cycling Shouldn’t Be Ignored
Although a cycling pump may still provide water, the long-term consequences can be significant. Constant starting and stopping increases electrical load, raises energy consumption, and accelerates wear on internal components.
Over time, this can lead to:
- Premature pump failure
- Burnt-out motors
- Pressure switch damage
- Reduced system efficiency
Addressing cycling early is usually far less costly than replacing a failed pump.
How the Cause Is Usually Identified
Diagnosing pump cycling involves more than simply observing the pump. Pressure readings, tank air charge, valve performance, and system layout all need to be assessed together.
At Citywide Plumbing, pump issues are typically investigated by checking pressure behaviour under different conditions, inspecting tanks and switches, and confirming whether pressure is holding when water use stops. This helps narrow down the issue before any repairs or replacements are considered.
What Fixes Usually Involve
The solution depends entirely on the cause. In some cases, restoring correct air pressure in the tank resolves the issue. In others, replacing a damaged pressure tank bladder, faulty pressure switch, or failed check valve is required.
If leaks or system design limitations are involved, repairs may extend beyond the pump itself. The key is identifying the underlying cause rather than treating the symptoms.
Final Thoughts
A water pump that keeps cycling is almost always trying to tell you something. Whether it’s a pressure tank issue, a leak, or a failing component, the behaviour is a signal that pressure isn’t being maintained as intended.
Understanding the cause early helps protect the pump, reduce energy use, and keep water supply reliable. If cycling becomes frequent or persistent, a proper assessment can prevent much bigger problems down the line.
