A check valve is basically allow fluids or gasses flow only in one direction and prevent opposite flow. It does not need any human as a way of working, it does it automatically. As long as the fluid flows, the disc inside remains open, if the fluid decreases or stops, the disc closes. If a flow comes from the opposite direction, the disc does not move. In this way, you can use your system as it should be.
For example, its function is similar to the diodes used in electricity.
Check valves operate at certain pressure values. If the fluid pressure rises above a certain level, the valve opens automatically. This opening pressure is called cracking pressure. If it falls below this pressure, it closes itself.
