Operating principle of Evac vacuum toilet
Pushing the flush button sends an air pulse to the control mechanism that connects the vacuum to the water and discharge valves. The water valve opens and lets rinsing water flow into the bowl through the flushing ring. After a short delay, the discharge valve opens and the contents of the bowl are discharged into the vacuum sewer. The control mechanism then closes the discharge valve and, after a short delay, closes the water valve. The delayed closing of the water valve ensures that a small amount of water remains at the bottom of the bowl. The toilet is then immediately ready for the next flush.