Gravity vs Pressure-Assisted Toilets

 In Plumbing

Ever spent a lot of time thinking about your toilet’s flushing mechanism? Probably not. Nevertheless, you may need to know how it works and the difference between the two types that are offered in order to understand how to troubleshoot and repair your toilet. Whether you prefer gravity-assisted or pressure-assisted flushing mechanisms, here are the pros and cons of each, including how they work.


These toilets are the most common variety and have been for a long time. Gravity-assisted toilets function through gravity, as their name implies. When you push the handle, a valve opens within the tank and the water falls from the force of gravity. As the water falls inside the bowl a siphoning effect is created in the trapway at the base of the toilet. This siphoning action moves water and waste through the pipe and into the septic tank or utility sewer pipes. Following this gravity-induced waste and water removal, a small gushing pipe refills the tank until a float shuts off the flow of water. To prevent overflow in the tank, there is also a small overflow tube to keep the water inside the tank.


Pressure-assisted toilets rely on the same gravity but assist the force of gravity with additional pressure. A small tank within the main tank supplies added pressure. This is achieved as water displaces air within a sealed cylindrical tank inside the larger ceramic tank. This cylinder is metal or plastic and helps to generate a larger force through air inside the cylinder. Flushing these toilets produces a loud whooshing sound characteristic of the air pressure being forced through the tank. These toilets hold more water and require a minimum water pressure of about 25 psi to operate most effectively and are becoming more popular as efficient toilets that can use less water and flush more efficiently.

Advantages and Disadvantages

Since gravity-assisted toilets are still the most common in households and many other locations, these are the type of toilets you will likely encounter the most. Pressure-assisted toilets however, are getting popular and are often found in industrial or commercial settings for their effectiveness. These toilets are highly efficient and are often cleaner since the bowl holds more water. They are also more expensive than gravity-assisted toilets, often by several hundred dollars. Replacing parts can also be more of a hassle since hardware stores may not regularly stock some of the parts. These toilets are also considerably louder than gravity-assisted toilets due to the air pressure involved in the flushing mechanism.

Gravity-assisted toilets are the most popular and most economical options as they are cheap and effective. In general, gravity toilets are more than sufficient to meet the needs of most household and commercial settings, but can be less than optimal in terms of sheer volume efficiency than pressure assisted varieties. For larger scale plumbing needs, gravity assisted toilets may be less than optimal.


Whichever toilet you decide is best for your needs, Shamrock Plumbing is prepared to help you install, maintain, and repair it. Don’t hesitate to give us a call at 801-505-9505!

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