Gravity vs Pressure Assisted Toilets

The flushing mechanism on your toilet is arguably not the most interesting aspect of home plumbing, but it is nonetheless essential to the operation of a critical plumbing device. Knowing exactly how your toilet works is helpful when you have to make repairs or troubleshoot a potential problem or make a new purchasing decision. There are two types of flushing mechanisms on toilets: gravity assisted and pressure assisted. In general, gravity assisted toilets are the type most people are familiar with since they are the most common variety of flushing mechanism. Here is a closer look at the two varieties and some pros and cons of each.

Gravity Assisted



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



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 toilet you will likely encounter with the most frequency. 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 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.