Can A Centrifugal Pump Run Backward?

One of the most common mistakes when operating a pump, believe it or not, is reverse rotation. This occurs if the pump uses reversible motors, which can run either forwards or backwards. In essence, the pump, which should operate clockwise, operates counterclockwise (or vice versa). In layman’s terms, it runs backward, which is a critical concern for any centrifugal pump rotation issue.

What Will Happen If Pump Rotation Direction Is Reversed?

What will happen if pump rotation direction is reversed is a question many operators face, especially during installation or maintenance. If your pump is wired improperly, you could be reducing flow by up to 70%. The impeller could jam or become unthreaded. If the centrifugal pump direction is reversed, the impeller and acorn nut can spin off in just a few seconds, causing damage to the pump’s components such as the bearings or seals. This could completely destroy your centrifugal pump if undetected. Read more about pump maintenance and preventing damage and in our comprehensive guide.

Symptoms of Water Pump Running Backwards

Detecting the symptoms of a water pump running backwards can be tricky. The shape of the impeller and design of the pump’s body can determine the path that liquid flows. When centrifugal pump rotation direction is incorrect, the impeller still forces the liquid out due to centrifugal force. This means that the liquid is still discharged from the pump, even if it’s rotating in reverse. Because of this, the flow doesn’t reverse, making reverse rotation hard to detect. Common symptoms include reduced flow rate, unusual vibrations, increased noise levels, and early seal or bearing failure.

The risk of reverse rotation is higher when putting in a new pump system, or replacing parts. To be safe, it’s best to check which way the impeller rotates before you start pumping.

How to Check Centrifugal Pump Rotation Direction

If the pump is uncoupled, you can perform a simple test called a “bump test,” where you bump the power to your pump for a split second to check the centrifugal pump rotation direction. Pumps that can rotate forwards or backwards will show the correct direction of rotation on the pump, usually seen on the casing, bearing frame, or motor.

Before doing the bump test, first check for rotation stickers showing which direction the centrifugal pump should run. Secondly, connect the three wires to the motor. Now, check to see if the shaft turns clockwise when you bump the power. If it rotates counterclockwise, you’ll need to try something different. Switch two of the three wires. You can then try the test again.

Avoiding Damage From Incorrect Centrifugal Pump Direction

This sounds really simple in theory. After all, what’s so difficult about switching a few leads? However, working with electrical wiring can be dangerous, both for you and your pump! Unless you really know what you’re doing, it might be safer to contact a qualified electrician.

Ensuring proper centrifugal pump direction is not just about performance but also about safety and equipment longevity. If you’re unsure about how to check the rotation of your centrifugal pump, call our toll-free number at 1-800- 367-4180. We have experts on hand to help you choose, install, and maintain a variety of equipment.