A safety valve functions by automatically opening when a system's pressure surpasses a preset threshold. Usually, a spring-loaded mechanism keeps the valve closed in usual circumstances. When the pressure reaches the predetermined limit, the force of the pressure acts against the spring tension, opening the valve and releasing the excess pressure. The valve is closed by the spring when the pressure reaches a safe level again.

The sole direction of fluid flow that a foot valve permits is into the pump. The suction generated by turning on the pump opens the valve, allowing fluid to pass through. The fluid in the pump and pipe cannot return to the source when the pump is switched off because the valve automatically closes. This guarantees that there is liquid in the pump, which is essential for starting up without priming.