Spring loaded internal flaps force fluids to flow one way

A closer look

Sometimes the simplest physical barrier is all it takes to govern massive systems. A non-return valve features a mechanical flap held perfectly shut by a spring. When fluid pushes against it with enough pressure, the spring compresses and the fluid flows. The second the pressure drops or the fluid tries to reverse, the spring aggressively snaps the door shut, ensuring the pipes never suffer the indignity of backward flow.