What Is Water Pump Short Cycling and Why Does it Happen?


A pump short cycling happens when the water pump continuously switches ON and OFF while pumping water. The obvious disadvantage of water pump short cycling is the irregular water flow and premature wear of the motor.

Water Pump Short Cycling – A Detailed Look


A well pump is an excellent example to understand the short cycling phenomenon. The pump turns ON as soon as the water level inside the reservoir gets low. Modern pumps use a pressure switch to gauge the water level in the reservoir.

In normal conditions, the pump begins to work when it senses that the pressure within the reservoir is low. Once enough water is pumped into the reservoir, its pressure rises, and the pump automatically turns off.

When a pump undergoes short cycling, it cannot accurately determine the pressure level within the reservoir and constantly starts switching between ON and OFF positions. This malfunctioning induces stress on the pump and its components and if a short cycling pump is not fixed in a timely manner, it can result in costly repairs.

Causes of Water Pump Short Cycling

Several possible reasons can cause the water pump to go on and off rapidly. Let’s look at some of the most common reasons that cause pump short cycling.

Faulty Water Pump Pressure Control Switch

As discussed, the pump pressure control switch is the component responsible for switching the pump ON or OFF. If this switch is faulty, it will result in a false-positive reading, causing the pump to fluctuate between ON and OFF positions without any significant change in water level.

A pump control switch usually fails due to:

Sedimentation of Impurities: If the well water consists of a high amount of debris like silt, the orifices in the pressure switch can get clogged, causing it to read faulty pressure values.

Burned Contacts: The pressure switch's electrical contacts may deteriorate over time, causing electrical shorts that will abruptly stop and restart the pump when in operation.

If you have a faulty pressure switch, replacing it should resolve the short cycling issues in your pump.

Too Much Air in the Reservoir Tank

Well pumps commonly use two major types of reservoir tanks: a bladder-type tank or a charged tank.

When the water gets pumped into the reservoir in a bladder-type tank, the bladder pushes against the water and creates the necessary pressure within the lines. In a traditional charged tank, the air pressure inside the tank is used to push water through the lines. However, too much pressure within the reservoir can lead to a problem. If the reservoir pressure is high initially, the pump will cut off much earlier than the optimum level.

For example, consider an empty tank with a capacity to handle the pressure of up to 60psi. With higher internal pressure without water, say 40psi, as opposed to the normal level of 20psi, the pump will continue to work until the cut-off pressure, 60psi. The pump cannot sense if the reservoir is over pressured. The solution to this problem is to vent out the pressure in the reservoir first and set it to factory levels.

Too Little Air in the Reservoir Tank

This type of malfunctioning happens with non-bladder-type reservoirs. These tanks depend on air pressure within to regulate the pressure switch. If the inside air pressure drops, the tank will not trigger the pressure switch correctly, causing the pump to switch ON and OFF erroneously.

Blocked Water Lines

Water lines run from the reservoir to the endpoints like taps or showers in your house. These lines, when clogged, can create higher internal pressure, causing the water pump to cut off abruptly even when there is room for more pressure.

Clogged lines are not an issue for new systems since clogging is a process that happens gradually, given that the sediment particles are smaller in size. However, if your water lines have been there for a while, it is best to get the lines checked out for blockages.

Need Help in Selecting the Right Pump?

Water pump short cycling adversely affects water flow and your pump’s health. Also, over-pressurized water reservoirs can turn dangerous if not handled properly. In such cases, it is best to seek professional help.

Hayes is a factory-trained and authorized repair center for a range of pump manufacturers. With years of troubleshooting experience, our highly skilled pump technicians can solve your pump issues swiftly. Contact us for repair help today!

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