Which combination of devices would you expect downstream of a pump to control pressure and protect the system from surges?

• A. Foot valve and strainer.
• B. Air relief valve and foot valve.
• C. Pressure sustaining valve and pressure relief valve.
• D. Y Strainer and suction piping.

Answer: (C)

Controlling pressure downstream of a pump requires devices that both prevent the pressure from dropping too low and protect the system from spikes. A pressure sustaining valve keeps the downstream pressure from falling below a set point by allowing flow when demand would otherwise cause a drop, acting as a minimum-pressure keeper. A pressure relief valve, on the other hand, opens to vent fluid when downstream pressure exceeds a chosen limit, preventing damage from surges or overpressure.

Used together downstream of a pump, these two devices provide balanced protection: the sustaining valve maintains a reliable operating pressure, while the relief valve clamps excessive pressure during surge conditions.

Components that sit on the suction side, like a foot valve or a strainer, don’t regulate discharge pressure or protect against surges. An air relief valve helps vent trapped air rather than control pressure, and a Y strainer with suction piping focuses on filtration and suction protection rather than downstream pressure control.