Troubleshooting Rotary Pump Problems

A rotary pump is a device that moves fluid through the principle of rotation. The pump creates a vacuum that sucks in water or any other liquid from a source. Because of its design and mechanism, it efficiently removes air from the supply lines, and therefore reduces the need to bleed trapped air out manually. However, problems do occur during operation. Try out the troubleshooting tips below before calling in a professional.

No Fluid is Dispensed

Check the direction of the rotation and reverse the motor if it is moving the wrong way. If the pump does not create sufficient suction, prime the pump by expelling gas from the supply line and introducing liquid in place of air. Inspect the pipework joints and see if there are any air leaks. Tighten the connections and ensure the leaks are repaired. Inspect the suction tube and fix obstructions. Remove the suction tube, clean the strainer located at the tube inlet and reinstall it.

Discharge is Irregular

Ensure that the NPSH is sufficient. Increase the diameter of the supply line and the suction head. Reduce the length of the supply line and simplify its configuration. Reduce speed if pump operation is too fast. Check the temperature of the liquid passing through the system and lower it if necessary.

Air leaks can also cause irregular discharges. Repair the joints on the pipework to prevent gas from entering the system. If there is any air trapped inside the supply line, prime the pump as detailed above. Check the fittings for any sign of blockage. Detach the fittings and clean the strainers.

Low Pump Capacity

Inspect the suction lines for any sign of damage. Repair leaks by either replacing the suction line or replacing the fittings. Inspect the rotor and vane. If they are excessively damaged or worn out, replace them with new ones. If the system is producing too much pressure, try simplifying the configuration of the supply lines.

This issue may also be caused by an obstruction in any part of the system. Check all parts of the system for any type of blockage or obstruction. Clean the parts that are obstructed especially the strainers in every fitting. If the pump's speed is too high, reduce it.


Overheating could be caused by too much speed or liquid temperature. Decrease the temperature of the liquid passing through to assist it or decrease the speed of the pump. If overheating is caused by too much pressure inside the system, clean obstructions in the supply lines. A worn-out pumping element should also be replaced to avoid this issue.


Check the food valve strainer for any sign of blockage and clean it. Trapped air is also a probable cause. Prime the pump if air causes noise. Decrease the pump's speed and lower the temperature of liquid passing through the supply lines. If pressure levels are soaring, service the fittings and fix clogs by removing trapped debris. Check the washers and lock nuts. Ensure that they are tightened securely. Replace them if they are worn out.