Power Flushing With Pressure-Assist Toilets

Many of today's best-performing low-flow toilets enhance their flush with air pressure to force water into the bowl at high speed.

In a standard (non-pressurized) gravity-flush toilet, water fills a tank behind and above the toilet bowl. When the toilet is flushed, a valve at the bottom of the tank opens and water flows from the tank into the bowl, producing the siphon-action flush.

With a pressure-assist toilet, instead of an open tank behind the toilet bowl there’s a sealed plastic vessel hidden inside the porcelain tank. After the toilet is flushed, the pressure vessel fills from the bottom using standard water pressure. As water (1.6 gallons or less, depending on the model) flows into the vessel, air in the tank is compressed above the water, “charging” the tank. No special pump or compressor is involved; water pressure creates the compressed air.

Published June 1, 2010

Wilson, A. (2010, June 1). Power Flushing With Pressure-Assist Toilets. Retrieved from