How the Vacuity toilet works

Water in the tank, vacuum tank and bowl are at their maximum levels.

Water level in the lower passage permits venting of air into the drain line.

When flush lever is activated, tank water passes through the outlet into the bowl rim. 

As water rushes into the bowl from the rim, water also passes down the trap, sealing the air vent.

After a few seconds, tank is empty, valve is closed and refill begins.

At the same time, water discharges from the vacuum tank, creating a vacuum in the upper portion of the passage way.

This vacuum draws water from the bowl into the trapway. 

After all water has passed through the rim, air is vacuumed into the trapway.

The vacuum tank refills, air is forced down the vacuum tube and into the lower passage.

The toilet is now ready for the next flush. 

Report on toilets

Vacuity toilet

Terry Love's Consumer Report on low-flow toilets