A foot valve is fitted on the suction line, placed at the bottom so it can hold a full column of water in the suction pipe. This keeps the line primed and prevents water from draining back into the source when the pump stops, so the next start is easier and quicker. It’s on the suction side because it’s purpose is to maintain prime and prevent backflow; putting a valve on the discharge line would obstruct pumping, and terms like supply or return aren’t where a foot valve is used.

In a synchronous motor the rotor speed is synchronized with the stator’s rotating magnetic field. The stator creates a magnetic field that rotates at the synchronous speed, which is determined by the supply frequency and the number of poles (Ns = 120 f / P). The rotor—fed with DC excitation or equipped with permanent magnets—locks to that rotating field and follows it in steady operation, so there is essentially no slip between rotor and field. This means the rotor turns at the same speed as the rotating magnetic field, not slower, faster, or stationary. For example, at 60 Hz with four poles, the synchronous speed is 1800 rpm, so the rotor runs at about 1800 rpm.

Priming a pump means removing air from the suction side so the pump can be filled with water and develop flow. When there’s no head on the suction side and no foot valve to hold a water column, gravity alone won’t keep the line primed. You need a source of suction to lift water from the source into the pump. A vacuum pump or ejector creates that suction by lowering the pressure at the pump entrance, drawing water up from the source and filling the suction line and pump casing, which achieves priming. An electric motor is just a drive, not a priming method. Gas pressure wouldn’t reliably create the necessary suction to lift water, and while a hand pump could be used for priming in some setups, the standard device for this scenario is a vacuum pump or ejector.

Regularly exercising valves keeps them operable and ready to isolate parts of the water system when needed. It prevents seizing from corrosion, deposits, or infrequent use, and it also verifies that the valve’s actuation devices, wiring, and position indication are working so operators can trust the control system during emergencies or maintenance. Critical valves—those whose operation affects large service areas or essential facilities—should be exercised on a yearly basis to maintain a reliable isolation capability. Non-critical valves can be scheduled less frequently, typically every two to three years, in line with policy, to balance reliability with available resources. This approach is proactive, not reactive, and it’s about ensuring readiness rather than surveying customers, replacing valves annually, or exercising only after a failure.