Siphonic Jet Toilet vs. Gravity-Fed Toilet

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Last Updated on July 27, 2022 by acechapman

Alright, so you are on the market for a new toilet. But, there are so many different types out there — which one do you choose? When it comes to flushing systems, some of the most popular models include the siphonic jet and the gravity-fed models. This is our siphonic jet vs. gravity-fed toilet comparison. This will help you find which type is best for you.

Siphonic Jet Toilets

Siphonic jet toilets are becoming increasingly popular and one reason for this is because they work really well. A siphonic jet toilet system is characterized by a reverse P- or S-shaped trap way. It’s one end being the inlet from the bowl, and the other connected to the plumbing in your home. This trap way is specifically designed to create a siphon that shoots the waste down the tubes.

How Do Siphonic Jet Toilets Work

Siphonic toilets work pretty simply because you press the flush lever. This sends the water from the tank into the bowl. You will then see the water rapidly rise in the bowl, then rapidly subside as it takes the waste with it. The water usually flows out of the tank faster than it can exit the bowl, which then creates this siphon action that pulls waste out.

As the water exits the bowl, it displaces the air and creates a vacuum that sucks the waste right out. This siphoning action is so strong that it can pull any solid waste right down with it. Towards the end of the flush, you will usually hear a gurgling noise. This means that the vacuum has been broken and the remnants of the tank water will then fill up the toilet bowl.

Water Usage and Design

Siphonic Jet vs. Gravity-Fed Toilet
Siphonic jet toilets usually use close to 4 gallons of water. But, there have been many water usage laws passed that often limit toilets to using no more than 1.6 gallons of water per flush. For this reason, the design of siphonic toilets had to be rethought. They would still work properly even with much less water being available per flush.

Features, Pros, and Cons

Siphonic toilets have some good features which you might appreciate. For one, you will be able to tell that it’s a siphonic toilet because they tend to have a very high water level in the bowl. The water in the bowl helps to seal noxious gasses in the plumbing below. You will notice that the water surface area in a siphonic toilet can be more than twice that of a gravity-fed model.

In terms of pros, siphonic toilets tend to have a cleaner bowl and are easier to clean, plus they don’t have as many skid marks either. Siphonic toilets also have a powerful yet quiet flush, they help save water, and they are virtually odorless. On the other hand, siphonic toilets, due to their long and narrow trap ways, are more prone to clogging than other types of toilets, plus they have a much large bowl and therefore take up a lot of space.

Gravity-Fed Toilets

Siphonic Jet vs. Gravity-Fed Toilet
Gravity-fed toilets are also becoming increasingly popular. This type of toilet is mostly seen in Europe but is slowly catching on in North America. This is a fairly good choice, especially if saving water is something that you are concerned with. These toilets use the force and gravity of water dropping straight down to flush out the bowl.

How Do Gravity-Fed Toilets Work

Gravity-fed toilets work very simply. Water is released from the tank and travels directly down into the bowl with a lot of force. These toilets feature a very short and wide, and virtually straight trap way. The sheer force and weight of the water force all matter out of the trap way. Washdown toilets tend to be clog-free, because their wide and short trap ways, combined with the force of the water, are not easy to clog. There are not many things that can easily clog the trap way of a gravity-fed toilet.
Water Usage

A big advantage of gravity-fed toilets is that they tend to be very friendly in terms of saving water. They generally come with a dual-flush system, so you can use one flush for liquid waste, which often uses under 1 gallon per flush, and you can use the heavier flush for solid waste, which usually uses 1.6 gallons per flush or less.

Features, Pros, and Cons

One big feature of the gravity-fed toilet is that they tend to be short and narrow, which is due to the design of the trap way. This means that this kind of toilet is usually better for smaller spaces, as they take up much less room than the siphonic counterpart.

The short and wide trap way allows for a lot of waste to flush easily, but what also needs to be said is that the water level in this type of toilet bowl tends to be quite low, and this often results in odors.

In terms of the advantages of gravity-fed toilets, they tend to be amazing at saving water, they are virtually impossible to clog, they don’t cost too much, and they have a compact design. On the other hand, due to the low water level in the bowl, these toilets don’t do a great job at keeping odors and gas in the pipes, and thus they can be a bit smelly.

These things also have a loud and noisy flush, and due to the design of the toilet, they often have skid marks and dirty bowls. If you put a really heavy load into the gravity-fed toilet, you might have to flush a couple of times.


There you have it folks, everything you need to know to choose between a siphonic jet and a gravity-fed toilet. As you can see, both have their advantages and drawbacks, so now it’s up to you to choose which one best suits your needs.

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