How a Pressure-Assisted Toilet Works

Bathroom interior
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Pressure-assisted toilets have come a long way over the years, with improvements in both flushing efficiency and noise reduction. Unlike standard gravity-fed toilets that depend on the force of gravity to flush when water is released from the tank, a pressure-assisted toilet uses compressed air to significantly boost the flushing power. The result is that you get a powerful flush with less water—about 1.1 to 1.4 gallons per flush (gpf)—compared to 1.6 gpf on a standard new toilet or 3. 5 to 5 gpf on many old toilets.

How a Pressure-Assisted Toilet Works

Pressure-assisted toilets look just like standard gravity-fed toilets...until you look inside the tank: Instead of a pool of water, there's just a sealed, plastic pressure tank. Inside the tank ​is water and air. As the tank fills with water during a refill cycle, the air inside the tank is compressed—merely by the power of the water pressure in the home's water supply.

When the toilet is flushed, the tank releases the water that's under pressure, creating a forceful blast into the toilet bowl, sort of like blowing water from a straw. The tank refills with air as the water is ejected. At the end of the flush, a fill valve automatically opens to refill the pressure tank with water, just like with a standard toilet.​

Benefits of Pressure-Assisted Toilets

The pressure-assisted design creates a strong flow of water that cleans the bowl better, removes waste better, and flushes more completely than a typical gravity-fed system. According to some estimates, pressure-assisted toilets also can flush 50 percent farther than gravity toilets, resulting in cleaner waste pipes and less chance of clogs down the road.

Another main benefit of pressure-assisted toilets is water savings. Compared to conventional modern toilets, pressure-assisted models can use about 12 to 30 percent less water. The savings compared to an old toilet, which can use upwards of 5 gallons per flush, are far greater. Where water savings may not be realized is when comparing to a dual-flush toilet, which can have flushes as low as 0.8 gpf (for liquids only).

Finally, pressure-assisted toilets don't sweat, which is a boon for people who live in hot, humid climates. Because the water is contained in a plastic tank—and not right up against the wall of the porcelain tank, as in standard toilets—condensation does not form on the front side of the tank.

Drawbacks of Pressure-Assisted Toilets

The primary downside to pressure-assisted toilets can be summed up with two words: loud flush. There really isn't an effective way to silence a blast of pressurized air and water ejecting from a tank that's contained in a porcelain vessel (that is, your toilet). The best way to deal with this is to close the lid of the toilet bowl before flushing.

Another drawback to pressure-assisted toilets is their relatively complex design. They have more parts and internal functions than gravity toilets, and that means more potential problems. Toilets can be fussy, and pressure-assisted models are no exception. And when things do go awry, it's generally not as easy to find parts for pressure-assisted systems, or as easy to make repairs. To be fair, it's hard to compete with standard gravity toilets in this regard, as most repairs with these involve nothing more than replacing a part that costs less than $10.