Why Does My Well Pump Keep Turning On and Off? Well Pump Short Cycling?

A well pump should run long enough to refill the pressure tank and then remain off while the stored water is used throughout the home.

When a pump starts and stops repeatedly within a short period, the system may be short cycling.

Short cycling is more than an annoyance. Every pump start places additional stress on the motor, pressure switch and electrical components. If the problem is ignored, it can shorten the life of the pump and lead to a more expensive repair.

What Is Well-Pump Short Cycling?

Short cycling occurs when a well pump turns on and off more frequently than it should.

In a properly operating system, water stored inside the pressure tank supplies the home between pump cycles. As the water is used, system pressure falls gradually until it reaches the pressure switch’s cut-in setting.

The pump then starts and runs until the pressure reaches the cut-out setting.

A typical system may operate at:

• 30 PSI cut-in and 50 PSI cut-out

• 40 PSI cut-in and 60 PSI cut-out

When the pressure tank cannot store the proper amount of water—or when the system is losing pressure—the pump may start after only a small amount of water is used.

In severe cases, the pump may click on and off every few seconds while a faucet is running.

Common Signs of a Short-Cycling Well Pump

A well system may be short cycling when:

• The pump starts every time a small amount of water is used

• The pressure switch clicks repeatedly

• The pressure gauge rises and falls rapidly

• Water pressure surges at faucets or showers

• The pump runs for only a few seconds at a time

• The pump cycles continuously while a toilet is filling

• The lights dim each time the pump starts

• The pressure tank feels unusually heavy or completely full of water

• The pump cycles even when nobody is using water

Short cycling should be investigated before replacing the pump. In many cases, the pump itself is not the original cause of the problem.

1. Incorrect Pressure-Tank Air Charge

One of the first things to check is the pressure tank’s air precharge.

Most modern pressure tanks contain a bladder or diaphragm that separates the compressed air from the system water.

The compressed air provides the force that pushes stored water back into the plumbing system.

For most bladder-style pressure tanks, the air pre-charge should be set approximately 2

PSI below the pressure switch’s cut-in setting.

Common pre-charge settings

• 30/50 pressure switch: approximately 28 PSI

• 40/60 pressure switch: approximately 38 PSI

The pump must be turned off and all water pressure must be drained from the system before checking the tank’s air pressure.

Checking the tank while the water side is still pressurized will not provide an accurate pre-charge reading.

What Happens When the Prec-harge Is Too High?

When the air charge is too high, the tank may contain very little usable water before the pressure falls to the pump’s starting point.

Possible symptoms include:

• A sudden drop in pressure

• A brief interruption in water flow

• Very little drawdown from the tank

• Frequent pump starts

• Rapid pressure changes

If the air pressure is equal to or higher than the switch’s cut-in pressure, the tank can empty before the pump starts.

What Happens When the Pre-charge Is Too Low?

A low air charge can also reduce the tank’s proper operating capacity.

Possible symptoms include:

• Frequent cycling

• Poor pressure performance

• Excessive movement of the bladder

• Reduced tank drawdown

• Premature tank wear

The air pre-charge must match the pressure switch setting—not simply the number printed on the side of the tank.

2. A Failed or Waterlogged Pressure Tank

A failed pressure tank is one of the most common causes of short cycling.

If the bladder or diaphragm inside the tank ruptures, the water and air are no longer properly separated. The tank may gradually fill with water and lose the compressed-air cushion required to store usable water.

A waterlogged tank provides very little drawdown. As soon as a fixture is opened, the pressure drops quickly and the pump starts.

The pump then reaches cut-out pressure rapidly because there is very little air space to compress.

This creates a repeated cycle of:

1. Pressure drops quickly

2. Pump starts

3. Pressure rises quickly

4. Pump stops

5. The process repeats

Signs of a Failed Pressure Tank

Possible signs include:

• Water coming from the tank’s air valve

• The tank feeling completely full and heavy

• The pump starting after only a few seconds of water use

• Very little water available between pump cycles

• Pressure rising and falling unusually fast

• The tank no longer holding its air pre-charge

If water comes out of the air valve, the internal bladder has likely failed and the tank normally requires replacement.

3. A Pressure Tank That Is Too Small

A pressure tank may be working properly but still be too small for the pump and household demand.

The size printed on the tank is not the amount of usable water it stores.

A pressure tank contains both compressed air and water. The actual usable water between pump cycles is called drawdown.

A tank with insufficient drawdown may cause the pump to start frequently during:

• Showers

• Laundry

• Lawn watering

• Large bathtub filling

• Multiple fixtures operating at once

• Water-treatment backwashing

The tank should be sized according to the pump’s flow rate, minimum recommended run time and the pressure-switch settings.

A larger pressure tank does not increase the pump’s pressure, but it can allow the pump to run longer and start less often.

4. A Clogged Pressure-Switch Nipple

The pressure switch must sense the water pressure inside the system.

It normally does this through a small threaded nipple or passage connected to the tank tee or pump piping.

Iron, sediment, rust and mineral deposits can partially block this small opening.

When the pressure switch cannot sense system pressure properly, it may:

• Start the pump late

• Shut the pump off late

• Cycle erratically

• Fail to start the pump

• Allow the pressure to rise beyond the expected cut-out point

• Cause pressure-switch chatter

The small pressure connection should be clean and unrestricted.

Replacing a pressure switch without checking the nipple beneath it may leave the original problem unresolved.

5. A Faulty or Improperly Adjusted Pressure Switch

The pressure switch controls when the pump starts and stops.

Inside the switch are electrical contacts, springs and mechanical components that respond to water pressure.

Over time, the contacts may become:

• Burned

• Pitted

• Worn

• Corroded

• Contaminated by insects or moisture

• Damaged by rapid cycling

A switch can also operate incorrectly when its settings have been adjusted without properly testing the complete system.

The pressure switch should be matched to:

• The pump’s pressure capability

• The pressure-tank precharge

• The plumbing system

• The intended cut-in and cut-out range

• The pump’s voltage and motor load

Installing a 40/60 pressure switch on a pump that can barely reach 60 PSI may cause the pump to run continuously rather than short cycle. However, incorrect switch settings can create several unusual pressure and cycling problems.

6. A Leaking Check Valve or Foot Valve

A check valve or foot valve is intended to prevent water from flowing backward when the pump shuts off.

If the valve leaks, system pressure may fall even when nobody is using water.

Once the pressure reaches the pressure switch’s cut-in setting, the pump starts again and rebuilds the pressure.

This may repeat throughout the day or night.

Signs of a Leaking Check Valve or Foot Valve

Possible signs include:

• The pump cycles when no fixtures are operating

• The pressure gauge slowly drops after the pump shuts off

• A jet pump repeatedly loses prime

• Air appears in the plumbing

• The pump starts unexpectedly overnight

• Pressure falls with the main house valve closed

A falling pressure gauge does not automatically prove the check valve is the problem.

The pressure loss could also be caused by a leaking waterline, plumbing fixture or well component.

The system should be isolated and tested before replacing parts.

7. A Leaking Underground Waterline

A leak between the well and the house can cause repeated pump cycling.

The leak may be located in:

• Buried poly pipe

• A pitless adapter connection

• A fitting inside the well

• A pipe joint

• The waterline entering the house

• A damaged section of pipe caused by frost or movement

  
  

Depending on the size of the leak, the pump may cycle occasionally or run almost continuously.

Possible warning signs include:

• Wet ground near the well or waterline

• Unexplained soft or muddy areas

• The pump cycling when no water is being used

• Reduced household pressure

• Increased electrical consumption

• Air or sediment entering the system

• A pressure gauge that steadily falls after shutdown

Not every underground leak will be visible at the surface, particularly when the soil is deep, porous or frozen.

8. A Plumbing Leak Inside the Home

A small plumbing leak can slowly lower system pressure and cause the well pump to start repeatedly.

Common causes include:

• A running toilet

• A dripping faucet

• A leaking outdoor hydrant

• A failed humidifier valve

• A leaking water-treatment drain valve

• A damaged appliance supply line

• A reverse-osmosis system constantly sending water to drain

• A leaking hot-water tank

• A cracked pipe in a crawlspace

A toilet that runs intermittently can be enough to trigger extra pump cycles throughout the day and night.

Before assuming the problem is inside the well, the home’s fixtures and water-using equipment should be inspected.

9. Water Flowing Back Into the Sump or Storage System

In systems involving cisterns, storage tanks or transfer pumps, a leaking check valve may allow water to return after the pump shuts off.

This can cause the float switch or pressure switch to reactivate the pump repeatedly.

The correct diagnosis depends on whether the pump is controlled by:

• A pressure switch

• A float switch

• A pump-control panel

• An electronic water-level sensor

• A combination of pressure and level controls

Understanding which control is actually starting the pump is essential before troubleshooting the system.

10. A Pump That Is Oversized for the Pressure Tank

A pump that produces a high flow rate can refill a small pressure tank very quickly.

The pump may reach cut-out pressure after running for only a few seconds.

Although the system may still supply water, frequent short operating cycles can increase wear on the motor and electrical components.

A properly designed system should provide enough tank drawdown to allow the pump to run for an appropriate length of time.

The solution may involve:

• Installing a larger pressure tank

• Adding additional tank capacity

• Correcting the existing tank precharge

• Reviewing the pressure settings

• Installing an appropriate pump-control system

• Confirming the pump is properly sized for the application

Why Short Cycling Is Hard on a Well Pump

Electric motors experience their greatest electrical and mechanical stress during startup.

Every time the pump starts:

• Electrical current increases

• Motor windings heat up

• Bearings and rotating components accelerate

• The pressure switch contacts open and close

• The pump experiences a sudden change in load

A pump designed to run for longer cycles may be started dozens or hundreds of extra times when the system is short cycling.

Over time, this can contribute to:

• Burned pressure-switch contacts

• Motor overheating

• Failed start components

• Control-box damage

• Premature pump failure

• Increased electrical consumption

• Reduced pressure-tank life

Correcting the cause early is usually far less expensive than replacing a damaged well pump.

How to Check for Short Cycling

A basic observation test can provide useful information.

Step 1: Stop All Water Use

Turn off faucets, appliances, outdoor hydrants and water-treatment equipment that may be using water.

Watch the pressure gauge after the pump shuts off.

If the pressure falls while no water is being used, the system may have a leak or failed check valve.

Step 2: Open a Faucet Slowly

Observe how much water can be used before the pump starts.

If the pump starts after only a very small amount of water, the tank may have insufficient drawdown.

Step 3: Watch the Pressure Gauge

The pressure should generally fall gradually toward cut-in and rise steadily toward cut-out.

A gauge that jumps, sticks or moves erratically may be inaccurate or may indicate a pressure-sensing problem.

Step 4: Time the Pump Cycle

Observe how long the pump runs from cut-in to cut-out.

A pump that runs for only a few seconds may have insufficient tank capacity or another system problem.

Step 5: Check the Tank Precharge Properly

Turn off the pump, drain all water pressure to zero and then check the tank’s air charge.

Do not adjust the tank while the water side remains pressurized.

Can You Keep Using Water When the Pump Is Short Cycling?

The system may continue supplying water temporarily, but short cycling should not be ignored.

Every additional start increases wear on the pump and switch.

If the cycling becomes severe, it may eventually cause:

• Loss of water

• A burned pressure switch

• A tripped breaker

• Pump overheating

• Motor or control-box failure

When the pump is switching on and off every few seconds, reducing water use until the system can be inspected may help prevent further damage.

Is the Pressure Tank Always the Problem?

No.

A failed or incorrectly charged pressure tank is one of the most common causes, but short cycling can also result from:

• Pressure loss

• Valve failure

• Underground leaks

• Improper switch settings

• Clogged pressure passages

• Plumbing leaks

• Incorrect pump or tank sizing

• Faulty pump controls

Replacing the tank without testing the complete system can lead to unnecessary expense and an unresolved problem.

A proper diagnosis should confirm:

• Actual cut-in and cut-out pressures

• Pressure-tank precharge

• Available tank drawdown

• Pump run time

• Whether pressure holds after shutdown

• The condition of the pressure switch and nipple

• Whether the pump can produce the required pressure

• Whether water is leaking back toward the well

Well-Pump Short-Cycling Service in Thunder Bay

A well pump that repeatedly turns on and off is warning that something in the system is not operating correctly.

Superior Water & Wells provides pressure-tank service, pressure-switch replacement, pump troubleshooting and complete rural water-system diagnostics throughout Thunder Bay and the surrounding area.

We serve rural homeowners, camps, cottages and lakefront properties throughout Shuniah, Neebing, Kakabeka Falls, Murillo, O’Connor, Nolalu, Pass Lake and the Highway 61 corridor.

Is your pump clicking repeatedly, losing pressure or turning on when nobody is using water?

Contact Superior Water & Wells for reliable rural water-system service.

Superior Water & Wells — Rural Water Done Right.