9 Types of Toilet Flush Systems

Jessica Stone
by Jessica Stone

Flush toilets have been in use for centuries, first being introduced back in 1598 by Sir John Harington. They operate by using water to flush waste through a drainpipe to another designated disposal location. Over the centuries, the efficiency, design, and flushing systems of these toilets have drastically improved to yield the modern toilets available today.

While most homeowners know that their toilets flush, few understand which system it uses. In fact, there are a number of different types of flushing systems.

Each of the major toilet manufacturers – such as Kohler, Toto, and American Standard – has designed their own flushing systems that allow their products to use less water, while still have a powerful enough flush to properly dispose of waste. Although most toilets use the gravity flush system, other common types of systems include the dual flush system, single flush system, pressure-assisted flush system, double cyclone system, and more.

9 Types of Toilet Flush Systems

When it comes to purchasing a new toilet, the fixture’s flushing system is one of the most important features to consider. Whether you want a quiet flush, something that is more eco-friendly, or want a clog-free toilet designed for bulk flushing, here are some of the different types of toilet flushing systems available on the market today.

1. Gravity Flush System

Of all the toilet flush systems, gravity flush systems are the most common and oldest type used. As the name indicates, these systems are powered by gravity and use the weight of the water itself to create the necessary flushing pressure. This pressure then forces the contents of the bowl out and into the trapway. Water flows from the tank mounted atop the bowl and moves to the bowl via gravity creating a force inside the bowl, causing the toilet trap to siphon out waste.

Although most water tanks are found directly on top of the bowl, some gravity systems feature an elevated cistern which increases the distance that the water has to travel to the bowl – thus maximizing the flushing pressure that is produced. After each flush, a siphonic effect clears the below before refilling it, which ensures that nothing gets trapped or clogged in the process.

Since there aren’t any complicated mechanisms involved in gravity flush systems, repairs and replacements are pretty straightforward. They also don’t emit any loud sounds and are one of the quietest types of toilet flush systems. Although gravity flush systems are among the oldest methods of toilet flushing, their timeless simplicity has kept them around.

Pros of Gravity Flush Systems
  • Inexpensive and easy to maintain
  • One of the quietest options
  • Improved efficiency options available
  • Simple design
Cons of Gravity Flush Systems
  • Prone to sweating
  • Underperformance leading to clogs

2. Dual Flush System

Because of their environmentally friendly design, dual flush toilet systems are quickly growing in popularity. They offer the ability to use more or less water, depending on the waste that you intend to flush. Two flush buttons, usually installed on the top of the tank, allow you to choose between a “partial” or a “full” flush. The full flush operates like any other toilet, using approximately 1.6 gallons of water. This button is designed to be used with solid waste, or a mixture of liquid and solid waste.

A partial flush, on the other hand, is meant for only liquid waste – using less water than the full flush button with only 1.1 gallons. When you press on one of the buttons, the valve seal lifts off which allows water to flow down to the bowl. Again, the amount of water will depend on which button you push.

Many countries around the world have adopted the dual flush system, and some have even required its installation in new constructions due to its remarkable water-saving abilities.

Pros of Dual Flush Systems
  • Eco-friendly, known for its water-saving qualities
  • Can save you money on your water bills
  • Ideal for areas with a short water supply
Cons of Dual Flush Systems
  • Some models have confusing buttons
  • More difficult to maintain than standard systems
  • More costly repairs
  • Requires more cleaning since the low flush option doesn’t rinse the bowl as much

3. Single Flush System

Single flush toilets are the most common version found in older houses and buildings. They feature a single flushing mechanism, which means that all types of waste are flushed with the same amount of water. Depending on the manufacturer and the model, the amount of water used could be as much as five gallons.

These toilet systems typically use a trip lever handle that is either mounted on the side or the front of the tank. This handle is connected to a lift chain, which is connected to a flapper. When you press the lever down, the chain lifts the flapper off of the flush valve, allowing water to flow into the bowl.

Most toilets offer a combination of a single flush system and a gravity flush system. However, with the invention of low-flow toilets, you can find single flush systems that are more economical.

These types of toilets are usually more common in both homes and workplaces since it’s easier to find replacement parts for them. Or, should a component inside of the tank break, oftentimes it can be repaired for a pretty cheap rate. Many consumers prefer single flush toilets for aesthetic purposes, favoring the traditional lever style over the buttons.

However, single-flush systems are notorious for using up more water than other alternatives, which makes them detrimental to the environment and costly for your utility bills.

Pros of Single Flush Systems
  • Easy to find replacement parts
  • Cheap repairs
  • Classic lever design
  • Easier to operate
Cons of Single Flush Systems
  • Less water-efficient than alternatives

4. Pressure-assisted Flush System

Pressure-assisted toilet flush systems operate similarly to gravity flush system, but they feature an additional mechanism that is used to force water into the toilet bowl with more pressure. These systems have a plastic pressure tank with an air-filled below that gets pressurized each time water starts to refill in the toilet’s ceramic tank.

Upon flushing, the compressed air inside of the balloon pushes water into the bowl at a higher flow rate than in a conventional gravity flush tank. This operation allows the system to use less water, while still being as strong as a gravity system or use the same amount of water more efficiently. Pressure-assisted flush systems are commonly seen in commercial settings due to their powerful flushing action making them less likely to clog.

Because these systems are less likely to clog, they are easier to maintain and the water pressure keeps the bowl cleaner. However, because of the additional force that is applied during each flush, pressure-assisted toilets tend to be much louder than other alternatives.

Pros of Pressure-assisted Flush Systems
  • Very powerful flush
  • Easy to maintain
  • Less prone to clogs
  • Keeps toilet bowl cleaner
Cons of Pressure-assisted Flush Systems
  • Extra force makes these systems noisy

5. Double Cyclone System

The double cyclone toilet flush system is a relatively new invention, designed by the toilet manufacturing company Toto. With this system, water flowing from the tank enters the bowl via two nozzles facing sideways and found at the top of the bowl. The two nozzles are backed by a propulsion system, allowing more water to pass through the tube.

What results is a centrifugal, cyclonic rinsing action inside of the bowl and a more efficient flush. This “cyclone” is created because of the direction in which the water enters the bowl. Since the nozzles face sideways, this allows the water to strike the bowl’s surface, resulting in a vortex-like flushing motion. Although the double cyclone system is its own distinct technique, some gravity flush mechanisms are used in the process.

Pros of Double Cyclone Flush Systems
  • Powerful flush, while also using less water
  • Simple design
  • High-efficiency system – uses only 1.28 gallons of water per flush
Cons of Double Cyclone Flush Systems
  • Can be difficult to find replacement parts
  • Exclusive to TOTO products

6. Tornado Flush System

Found in newer Toto toilets, the tornado flush system is an improvement on the double cyclone toilet flush system. Instead of using two nozzles, the tornado system filters water into the bowl using three jets that are positioned sideways around the top of the bowl. As water enters the toilet bowl, it swirls around aggressively in a motion that resembles a tornado. This system is very effective at cleaning the bowl and also offers a quieter flush.

With tornado toilet flush systems, the toilet bowl lacks a rim which eliminates a breeding ground for germs and makes the toilet easier to clean.

Pros of Tornado Flush Systems
  • Effective at cleaning the bowl
  • Lack of rim makes cleaner easier
  • Quieter flush
Cons of Tornado Flush Systems
  • May be hard to find replacement parts
  • Exclusive to TOTO products

7. Tower Style Flush System

Also referred to as a canister toilet flush system, the tower-style system is primarily used in toilets manufactured by Kohler. The system features a canister toilet flapper which is typically mounted in the center of the tank and connected to the flush handle. Unlike a traditional flapper-type system, the tower-style lifts off completely and allows water to flow into the bowl from all 360 degrees.

As a result, the water is able to flow to the bowl quicker and create a much stronger flush. Kohler’s Class Five flushing technology uses a tower-style flushing system. They feature a flush valve that is designed in a way that the entry is bigger than the exit by 3:2. This design lets the system move more water, building up pressure and causing a powerful flushing action.

Pros of Tower Style Flush Systems
  • Faster and more efficient flush
  • Deposits a lot of water in the bowl
  • Requires little maintenance
  • Longer lifespan
Cons of Tower Style Flush Systems
  • Valves are complicated and require unique components to function
  • Expensive
  • Can be challenging to fix and/or replace

8. Rear Flush System/ Upflush Toilets

Also referred to as an upflush or macerating flushing mechanism, the rear flushing system is found in upflush toilets. These types of toilets feature a separate macerator chamber where solid waste is ground up and then channeled out of the toilet bowl. Although less common, rear flush systems are ideal for compromised spaces, like basements, or in settings where the toilet does not have a tank.

They offer a very sleek appearance, as fixtures and plumbing components are hidden and they usually have a different type of bowl than the standard variety.

Upflush toilets are designed to eliminate the need to install expensive plumbing. The primary difference between this type of toilet and conventional fixtures is the discharge system. The key components of this system are the macerator and a small diameter pipe.

The macerator features a rotating blade that grinds and shreds up human waste and toilet paper. Once combine with flushing water, solid material forms a slurry that moves effortlessly upward through a narrow pipe.

A quiet electric-powered pump moves this slurry upwards under pressure and through the small-diameter discharge pipe and to your normal sewage system. This pipe solves many structural concerns as it can be installed nearly anywhere.

Pros of Rear Flush System
  • Sleek, modern appearance
  • Powerful flush
  • Eliminates the need to install additional plumbing
Cons of Rear Flush System
  • Requires regular maintenance and adjustments to the system

9. Siphonic Flush System

Most siphonic toilets will feature a long, narrow reverse ‘S’ or ‘P’ shaped trapway. One end will serve as the inlet in the bowl, while the other is connected to the drain pipe beneath the bowl. This trapway design is meant to create a siphon. Once you push down on the lever or press a flush button, the flush valve opens to let the tank water to flow through the bowl. In regards to a siphonic flush system, you’ll usually see the water rise in the bowl and then subside rapidly into the outlet.

What is occurring here is that the water is flowing out faster from the tank than it can exit the bowl. As water exits out the trapway, it displaces air to form a vacuum. Then, when it flows over the kink in the trapway, the siphon begins. This type of flush system is incredibly common in the United States.

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Jessica Stone
Jessica Stone

Jessica considers herself a home improvement and design enthusiast. She grew up surrounded by constant home improvement projects and owes most of what she knows to helping her dad renovate her childhood home. Being a Los Angeles resident, Jessica spends a lot of her time looking for her next DIY project and sharing her love for home design.

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