What is the main purpose of a foot valve in a centrifugal pump?

The main purpose of a foot valve in a centrifugal pump is to prevent liquid from flowing back down the suction line. A foot valve is typically installed at the bottom of the suction line, submerged in the liquid to be pumped. When the pump is operating, the foot valve remains closed, allowing the liquid to be drawn into the pump while preventing it from returning back down the line when the pump is turned off. This is crucial for maintaining the pump's prime and ensuring that it can operate efficiently without needing to re-prime after every stop.

By preventing backflow, the foot valve also aids in reducing the effort required to start the pump again, as it maintains the liquid column in the suction line. This functionality is particularly important in systems where maintaining a constant supply of liquid at the pump’s inlet is necessary for effective operation. The importance of the foot valve cannot be overstated, as its failure to function correctly can lead to air entering the suction line and causing the pump to lose its prime, ultimately compromising the pumping system’s efficiency.