Why Does Your Rainwater Tank Pump Keep Turning On and Off?

Insufficient Water Supply

One of the primary reasons why a rainwater tank pump may keep turning on and off is an insufficient water supply in the tank. If the tank is not filling up as expected, the pump will continuously try to draw water, only to turn off again when the tank level drops below the pump’s intake.
This scenario can occur for several reasons, such as a blockage in the tank’s inlet or overflow pipes, a malfunctioning diverter, or even a prolonged dry spell that has depleted the tank’s water reserves. When the pump senses that the water level has dropped below a certain point, it will turn on to try and replenish the supply, but as soon as the water level drops again, the pump will turn off, leading to the constant cycling behaviour.

To address this issue, call a professional to inspect the tank’s inlet and overflow pipes for any blockages or obstructions that may be preventing the tank from filling up properly. A professional plumber may also suggest clearing any debris or vegetation that may be hindering the water flow. Additionally, they will check the tank’s diverter to ensure it is functioning correctly and to direct the rainwater into the tank as intended. If the issue persists, a plumber may recommend increasing the tank’s capacity or finding alternative sources of water to supplement the rainwater supply.

Pressure Switch Problems

Another common cause of a rainwater tank pump’s constant on-and-off cycling is a problem with the pressure switch. The pressure switch is a critical component of the system, responsible for monitoring the pressure within the plumbing and signalling the pump to turn on and off as needed.

Over time, these pressure switches can wear out, become clogged with debris, or simply malfunction, leading to erratic behaviour from the pump. If the pressure switch is not accurately detecting the system’s pressure, it may signal the pump to turn on and off even when the water supply is adequate, causing the short-cycling issue.

A professional plumber will inspect the switch for any visible signs of damage or wear and tear. If the switch appears to be in good condition, an adjustment of the pressure settings may be needed. It’s important to follow the manufacturer’s instructions carefully when making any adjustments or replacements to ensure the proper operation of the pressure switch and the overall system. Call a professional to do fix your rainwater system for you!

Airlock in the System

Another potential cause of a rainwater tank pump’s constant on-and-off cycling is an airlock in the system. An airlock occurs when air becomes trapped in the plumbing, preventing the smooth flow of water and disrupting the pump’s normal operation.

Airlocks can happen for various reasons, such as a leak in the system, improper installation, or even the introduction of air during maintenance or repairs. When an airlock is present, the pump may struggle to draw water, causing it to turn on and off repeatedly as it attempts to overcome the obstruction.

To address an airlock issue, you’ll need to identify and release the trapped air from the system. This can often be done by running the pump for a short period, which can help to dislodge the air bubble. You can also try manually bleeding the system by opening a tap or valve at the highest point in the plumbing to allow the air to escape. If the airlock persists, you may need to call the help of a professional to inspect and purge the system thoroughly.

Pump Size and Capacity

The size and capacity of your rainwater tank pump can also play a role in the constant on-and-off cycling behaviour. If the pump is not properly sized for the specific requirements of your rainwater system, it may struggle to keep up with the demand, leading to the short-cycling issue.

For example, if the pump is too small for the size of your tank or the number of fixtures it needs to supply, it may turn on and off frequently as it attempts to meet the water demand. Conversely, if the pump is oversized for the system, it may cycle on and off as it struggles to regulate the pressure and flow.

To ensure your rainwater tank pump is properly sized, consult the manufacturer’s recommendations or seek the advice of a professional installer. They can help you determine the appropriate pump size based on factors such as the tank capacity, the number of fixtures, the water usage patterns, and the overall system design. Replacing the pump with a correctly sized model can help to resolve the constant on-and-off cycling problem.