There are three primary types of toilets:

Gravity-Assisted (Typical residential toilet)

How It Works: Flush is powered by gravity since the tank is positioned above the bowl. A flapper valve at the bottom of the toilet tank controls the flush. The tank refills through a ballcock or fill valve, which closes when the water reaches the proper level – usually controlled by a float ball. As the tank refills, a portion of the refill water is diverted through a tube to refill the toilet bowl

Pros: Quiet, stable design. Most commonly used toilet technology in residential applications, as well as some small-scale commercial.

Cons: Consumer Report tests found models that perform as well as Pressure-Assisted types cost as much, while lower end models are not as effective.

Initial Cost: $225 to $300 for most (2006 dollars).

Modified Versions:
Better Gravity Flush
Flapperless Gravity Flush

Click here to read about these modified versions.

Pressure-Assisted

How It Works: The basic system has a separate, airtight tank inside the conventional looking tank. As the airtight plastic tank refills after flushing, air is pressurized above the water. During the flush cycle, this pressurized air rapidly pushes the water out of the tank. The water is delivered very quickly and at a high velocity – with a loud whoosh.

Pros: Consumer Reports found that pressure-assisted toilets have the fewest clogs.

Cons: Loud. Historically, this type of toilet has been too loud for multi-family residential use. Consumer Reports also found that dual-flush toilets provided substandard results when using the optional, .8 gallon mode.

Initial Cost: $225 to $300 for most (2006 dollars).

Modified Versions:
Air Pressurized Flush
Flushometer-Valve
Dual Flush Toilets

Click here to read about these modified verisons.

Vacuum Assisted

How it Works: Waste is pulled out of the bowl rather than being pushed. Inside the tank, there are two airtight plastic vessels: the flush-water tank and a vacuum tank, which is connected by a tube to an air-filled portion of the swan-neck trapway. When the toilet is flushed, the air vent in the trapway becomes sealed by the draining water. At the same time, water draining from the vacuum tank creates a vacuum that is transmitted to the airspace in the trap way. This modest vacuum force combines with the inherent siphonic action of the bowl to enhance the “pull” on the toilet bowl contents, boosting the flush.

Pros: Very quiet.

Cons: Fewer choices and models available. Consumer Reports also found that the latest models yielded less flushing power than pressure-assisted models but cost the same.

Initial Cost: $150 to $300 for most (2006 dollars).

Click here to read about this modified verisons.