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Gravity vs pressure assisted toilets

Marion Rosenfeld

There are several types of toilets on the market today. Toilets have different designs, they can either be made of a single or several pieces of material, they have different types and styles of bowls, they consume different amounts of water and the list goes on and on.

But when it comes to flushing systems, we can classify them to gravity and pressure assisted.

Which one is better and more efficient? Which one has a longer lifespan and which one is more affordable?

This article will tell you everything you need to know about what type of flushing system is the best for your needs and budget.

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Gravity toilets

gravity-fed flushing system

Most toilets on the market are equipped with gravity-fed flushing systems. It’s a system that has been around ever since flushing toilets were invented and it’s very unlikely that another system will replace it anytime soon.

How does it work

The flushing process starts with a push on the flush button. Once you push on the button, the flush valve that’s located inside of the toilet tank gets lifted and the water from the tank starts its way through the siphon.

The water usually enters the bowl through rim holes that are located under the rim. Because the water is dropped from height, it creates force of gravity which allows it to push the waste through the waste pipe into the septic tank.

Once the flushing process is completed, the water supply pipe starts filling the water tank until the in-built float valve shuts the flow off when the water level is sufficient.

With that said, there are several variations of gravity flushing system and here are some of the most notable ones.

Double Cyclone flushing system

double cyclone flushing system

The Double Cyclone is a flushing system that was invented by the largest toilet manufacturer in the world known as Toto. Toilets with Double Cyclone system feature rimless design. Instead of rim holes that spread the water around the bowl, there are two nozzles located at the side of the bowl. Once the water comes out through the nozzles, it moves down the bowl like a spiral at high speed. This creates centrifugal force which has more force than normal gravity flush which means that it’s able to clean the surface of the bowl more thoroughly with less water used.

One of the finest examples of toilets with Double Cyclone flushing system is the TOTO Vespin II. It uses 1 gallon of water per flush while delivers a powerful flushing action and doesn’t make as much noise as most toilets with traditional gravity-fed flushing systems on the market.

Dual flush

A common misconception is that toilet with dual flush system have double the flushing power and double the water consumption, but that’s not the case.

dual flush system

Toilets with dual flush system such as the Woodbridge T-0001 offer the option of using partial or full flush. The full flush is usually used for solid waste while the partial flush is used for liquid waste and other occasions when you don’t need the maximum flushing power.

The partial flush usually uses anywhere from about 60% to 80% of the water tank capacity. If partial flush uses 1 gallon of water during each flush, the full flush uses 1.28 or 1.6 gallons of water. This can save about 30% of water annually which can be seen in a few numbers shaved off the water bills each month.

Advantages of gravity-fed toilets

  • Proven to work. This type of toilets has been around for decades. They say that you shouldn’t fix what isn’t broken, and gravity assisted toilets have been proven to be efficient enough for regular use.
  • They are simple and usually easy to repair. Almost every “do it yourself” enthusiast knows how to fix majority of the most common toilet problems without hiring a professional plumber.
  • The affordable option. They are more affordable than pressure assisted ones and most of the replacement parts are usually cheaper as well.

Gravity assisted toilets have been around for decades. They say that you don’t fix what isn’t broken, so it’s not a surprise that they are still the number one choice of homeowners throughout the world.

What about the downsides?

We could say that gravity assisted toilets have no downsides, but that’s the same thing we were saying about dry toilets not so long ago.

Pressure assisted toilets – how do they work?

pressure tank

Toilets with pressure assisted flushing systems are relatively new and they were never nearly as popular as systems that rely on the force of gravity.

Toilets with pressure assisted flushing systems used to be expensive and they were mostly used in commercial places such as restaurants and sports stadiums. However, the recent advancement in technology allowed manufacturers to manufacture them at lower cost and the difference in price between toilets with gravity and pressure assisted flushing systems became smaller.

How do they work?

Pressure assisted toilets use a combination of water and pressurized air. They feature a water tank and a compression tank which is usually located inside of the water tank.

Once the water tank gets filled with water, the compression tank gets filled with air at the same time. When the flushing action starts, the water from the water tank fills up the bowl and pressurized air sucks the waste through the waste pipes. This creates more force than relying on gravity alone which means that pressure assisted toilets are able to flush down more waste at once.

Advantages of pressure assist toilets

  • Efficiency. Pressure assisted toilets are able to push more waste down the drain and that’s why they are more popular in commercial facilities where they are used by many people each day.
  • They don’t use as much water. Because they get additional pressure from air, they don’t need as much water as gravity assist toilets to have the same flushing efficiency. If we put it in numbers, a pressure assisted toilet consumes about 20% less water on average.
  • They are smaller. While that’s not the case for all pressure assisted toilet, some of them are smaller which often makes them more appropriate for smaller bathrooms.

What about the downsides?

Pressure assisted flushing systems have a few minor and a few huge downsides which is the reason why they never became as popular as gravity flushing systems.

The main downside is that toilets with pressure assisted flushing systems cost more. They are also made of more parts that that can start malfunctioning and most of the flushing parts are not easy to replace. Of course a toilet with compression tank can work well for years or decades, but more technology involved creates more chances of something going wrong.

On top of that, average “do it yourself” skills are usually not enough to fix the pressure assisted toilet when something start malfunctioning and there’s a good chance that you will need help from a professional plumber. If however you know how to fix just about everything, there’s a chance that you will have to wait for a week or two for factory parts.

Another downside of the pressure flushing systems is the noise. Today’s gravity-fed toilets are reasonably quiet and they don’t produce as much noise as older toilets that used over twice as much water during each flush. Pressure assisted toilets are another story and they can get quite loud during the flushing process.

The final downside is that the pressure can shred the toilet paper into pieces and shredded toilet paper sometimes doesn’t get flushed completely. This can create clogs which is the last thing most homeowners want.

Which one to buy?

At this point you have probably already decided whether to buy a toilet with gravity-fed or pressure-assisted flushing system. But here are a couple of suggestions just in case you haven’t made your mind up just yet.

What’s your budget?

Despite the fact that pressure assisted flushing systems got cheaper in the recent years, they are still quite expensive compared to gravity assisted ones. Is having a slightly better flushing performance worth a couple of extra bucks?

How much do you appreciate silence?

Pressure assisted flushing system is usually loud and can wake a few people up early in the morning. If you often use the toilet while other residents in your house are asleep, they will probably hate you for buying a pressure-assisted toilet.

Is there a warranty on the compression tank?

Air pressure tanks can be more expensive to repair than all the other toilet parts combined. A good pressure tank should work well for at least 10 years before something goes wrong, but sometimes there’s no guarantee that it won’t start malfunctioning sooner. A good warranty coverage is essential for making a great buy that won’t become a nightmare for your wallet.

Do you really need it?

Gravity assisted toilet does the job just fine in over 99% cases. Pressure assisted toilets are mostly used in commercial places and there’s a good reason for that.

What do we think?

We believe that pressure assisted toilets are unnecessary unless the toilet is in a place where dozens of people flush several pounds of waste each day.

We would even go as far as saying that a lot of manufacturers had poorly designed gravity-fed toilets on the market and they decided to equip them with pressure-assisted flushing systems in a hurry just to be compliant with newer water regulations and prevent clogging which happened often due to poor design of their toilets.

The truth is that today’s high-end toilets with advanced gravity flushing system are about equally effective as most toilets that rely on the power of pressurized air. They consume similar amounts of water and they have two huge advantages that are impossible to overlook. They offer flushing action with much less noise, and they are easier and cheaper to repair if something starts malfunctioning.

Instead of going for pressure assisted toilet, check out some of the best gravity fed toilets on our website and forget about the possibility of having problems with the compression tank in your lifetime.