Operating principle of Evac elongated vacuum toilet
The cavity behind the bowl houses the backplate assembly with the basic working components: the control valve, vacuum breaker, and water valve. The discharge valve is attached to the wall with a brace plate. The control valve sequences the entire flushing cycle. The vacuum sewer piping is under vacuum at a pressure of approximately 15 inHg. When the flush button is pressed, the control valve opens the discharge and water valves for a few seconds. Air at atmospheric pressure forces the contents of the bowl through the discharge valve and into the piping. In the piping, waste forms a slug that is propelled to the collection tank by the expanding air. The discharge valve closes first, then the water valve closes after it supplies washing and pool water. The controls are automatically reset after each flushing cycle.