Tankless Toilets – How they Work and Everything Else

Last Updated on May 18, 2022 by toilethaven

How Does a Tankless Toilet Work?

In order to flush a toilet, a large volume of water must be dumped inside the bowl at once. Since most homes water supply does not have sufficient pressure to do that, a toilet tank therefore becomes a necessity.

You might however noticed that toilets in public restrooms and especially urinals do not have a tank. Modern residential toilets do not also have a tank. So, how does a tankless toilet work?

Tankless toilets are toilets that do not have a water tank on top of the bowl and instead use water under high pressure straight from the supply line to flush the toilet. In buildings where the water pressure is not sufficient, tankless toilets are installed with a small water pump.

Although tankless toilets are mostly used in public restrooms, you can also install a tankless toilet in your home. Residential tankless toilets are in most cases smart toilets as well where they combine they combine their tankless design with other features like bidet seats and auto-opening/closing seats.

Unlike gravity flush toilets which depend on water from a tank, tankless toilets use pressurized water from to flush a toilet hence they need a pump. As a result, tankless toilets have a very strong flush and hardly ever clogs.

The advantages of tankless toilets is that they are space-efficient and that unlike a gravity flush toilets, you don need to wait for them to refill, making them effective for busy establishments. They are also not likely to clog.

Tankless toilets are more expensive than ordinary tank toilets, especially residential tankless toilets which also tend to be smart toilets. They are also dependent on electricity which is not cheap as well, and are therefore not usable if there is a power blackout.

Tankless toilets are calibrated to release a metered amount of water during each flush. They are usually more water-efficient than gravity flush toilets.

Residential tankless toilets are also known as smart toilets or bidet toilet combos. Apart from being tankless, they come with a bidet toilet seat and are so sleek and stylish. Read more here.

Tankless Toilets vs Tank Toilets


To properly understand how a tankless toilet works, let us first look at how a tank toilet works and the reason why a toilet tank is important.

Tank toilets are also known as gravity flush toilets. This is because the toilet tank is installed n top of the tank and thus the water flows from the tank to the bowl using gravity during flushing. Unlike tankless toilets, tank toilets do not need electricity to run.

The toilet tank is connected to the main water supply by a water supply line at the shut off valve. This makes sure that the tank is always full of water and ready to use.

Tank toilets use different amounts of water to flush the toilet. Old models can use up to 3.5 gallons per flush while newer models use 1.6 or 1.28 gallons per flush.

To flush a tank toilet, you pull a trip level located on the side of front of the tank. Dual flush toilets use buttons mounted at the top of the tank.

During flushing, water leaves the tank through an opening at the bottom called a flush valve to enter the bowl. The flush valve is afterwards sealed off by the toilet flapper allowing the tank to refill.

Tankless toilets are flushed using a device called a flushometer. A metered volume of water sufficient to flush the toilet is released every time you push the flushometer.

Residential smart tankless toilets have automatic flushing systems while some use a wireless remote control. Some also combine the 2 functions.

Due to the lack of a toilet tank, tankless toilets have few leaks (if any a toilet) and hence fewer repairs than tank toilets. They are also more compact making them ideal for small bathrooms.

Tankless Toilets vs Pressure-Assisted Toilets

Tankless toilets should not be compared with pressure-assisted toilets. Although some have a pressure-assisted flushing system, they are not what are known as pressure-assisted toilets.

Pressure-assisted toilets are tank toilets which look exactly like gravity flush toilets but do not 100% rely on gravity to help them flush. They have a secondary tank inside the main toilet tank called a pressure vessel.

Water flowing from the supply line enters this pressure vessel where there is air trapped and compresses it. The water is therefore stored inside the tank under pressure.

When you flush the toilet, pressurized water is dumped inside the bowl forcefully and the process starts once again in the pressure vessel. As a result, pressure-assisted toilets are louder than ordinary gravity flush toilets.

Pressure-assisted toilets are especially help for people looking to install read discharge toilets. In rear discharge toilets, waste exit the toilet from the back instead of the floor.

Rear discharge which are also known as rear outlet toilets therefore have a shorter toilet trap which is not enough to initiate a strong enough siphon action. Pressure-assisted toilet system comes in to give them the extra oomph.

Read more on pressure-assisted toilets here.

Tankless Toilets vs Wall-Hung Toilets


Another type of toilet that should not be confused with tankless toilets is wall-hung toilets, also known as wall-mounted toilets. They more look like they are tankless but they actually have a tank.

Wall-hung toilets are mounted on the bathroom wall unlike other toilets that are floor-mounted. Their toilet tanks are concealed in the bathroom wall such that only the bowl is visible.

To install a wall-hung toilet, a frame called a carrier is installed on the bathroom wall. The carrier is used to “carry” the toilet tank and is also where the bowl is mounted using long bolts.

To conceal, the toilet tank and the carrier, a secondary wall is erected inside the bathroom, leaving only a small opening where the flush buttons are mounted. This opening also gives you access to the toilet tank in case you need to carry out any repairs.

Unlike wall-hung toilets, tankless toilets are floor mounted and do not need a tank carrier or the erection of a secondary bathroom wall.

Read more on wall-hung toilets here

Pros and Cons of Tankless Toilets

Toto Neorest

The Pros

  1. Space-efficient
  2. Fast flushing system
  3. Sleek design
  4. Environment-friendly
  5. Few problems
  6. Easy to clean
  7. Powerful flush

The Cons

  1. Dependent on electricity
  2. Hard to repair
  3. They are expensive
  4. Noisy flushing

Benefits of a Tankless Toilet

The following are the pros/benefits/advantages of installing a tankless toilet over a tank toilet.

Space Efficiency

It is possible to install a tankless toilet in a small bathroom without it look stuffy. If anything, a tankless toilet will actually make a small bathroom look big. You can use up the extra space to spruce up your bathroom which will improve its overall décor.

One thing to remember is that tank toilets are wider than tankless toilets because of the tank, which also makes them longer. The absence of the tank also makes tankless toilets way shorter than tank toilets.

People with small bathrooms will find tankless toilets to be a great option.

Fast Flushing

In a tank toilet, after every flush you have to wait for the tank to refill before you can flush again. It is even worse if the waste was not cleared in the first round and you have to wait for the tank to refill before attempting again.

Tankless toilets do not need to refill. They are always ready to use. This makes tankless toilets the best choice for a bathroom with many users.

Sleek Design

Although it is not impossible to find a sleek tank toilets, tankless toilets definitely take the price. They are elegant, stylish and modern and will without a doubt complement any bathroom design.

As I had said before, residential tankless toilets use bidet seats which just like the toilets are beautifully designed. Bidet seats are more solid than the regular toilet seats and hence fit the toilet perfectly further enhancing its beauty.


Tank toilet owners will from time to time have to deal with a constantly running toilet, leaking toilet, overflowing toilet, low levels of water in tank and bowl and other issues from time to time. All this problems emanate from the toilet tank.

When you have a tankless toilets the above problems will be unheard off. Every amount of water that enters the bowl is metered and hence precise, without the possibility of leaking.

A leaking/running toilet is not only bad for the environment but it is also bad for your pocket.

Fewer Problems

A toilet tank has very many parts inside which fail/wear out after sometime necessitating replacements. Seeing that tankless toilets have fewer parts, they tend to have fewer problem to fix.

Few problems means few repairs. A tankless toilet has few moving parts therefore wear and tear is not something owners have to deal with.

Once you install a tankless it will serve you for long time before you are required to do any maintenance on it.

Easy to Clean

 Tankless toilet has few nooks and crannies compared to a tank toilet. Cleaning and maintaining the general hygiene of the toilet is therefore very easy and fast.

Their bowls are mostly fully skirted meaning dirt has nowhere to hide. This is not always the case with tank toilets. The gap between the tank and the bowl in two-piece toilets for instance is very hard to reach during cleaning.

Powerful Flush

While using a tank toilet, you are never sure if the first flush will do the job or not. You must wait for a confirmation.

With a tankless toilet the mess is taken care of in the first round. The water pressure is enough to push all the waste through the trap and down the drainpipe.

Tankless Toilets Problems

So, what are the disadvantages of installing tankless toilets? Here are some of them:

Dependent on Electricity

Tankless toilets needs connection to an electrical outlet to power the water pump. Without electricity, you can only flush the toilet with a bucket of water.

If you live in an area prone to power outages, the joy of owning a tankless toilet will be short-lived. You may be required to have a standby generator, which is not always cheap.

You will also start more in power bills after installing a tankless toilet. Apart from the power required to run the power, the bidet seat will also need to be connected to power to run its functions like hot water cleansing, warm air drying, heated seat, nightlight etc.

Hard to Repair

It is very easy to fix a gravity flush toilet. The same cannot be said of tankless toilets. You will need to bring in a professional plumber to help in with any issues that may arise.

Their replacements parts are also not readily available compared to a tank toilet’s parts and also tend to be more pricey.

They are Expensive

Tankless toilets cost way more than gravity flush toilets. These is not surprising when you consider all of their features relative to those of gravity flush toilets.

For comparison purposes, consider Toto Ultramax II, which is one of the best gravity flush toilet. Now compare it with the Toto Neorest 750H tankless toilet. The cost of the Toto Neorest 750H is more than 10 times that of the Ultramax II.

There are however cheaper tankless toilets especially those without bidet functions.

 They are Noisy

The flush water in a tankless toilet gashes out and cleans the toilet forcefully. As a result they tend to be very noisy. This has to be considered before they are installed

The noise will however concern you for the first few days but a after a while you will get used to it.

Tankless Toilets For Small Bathrooms

Do you have a small bathroom that you need to install a tankless toilet? One of the best tankless toilet for a small bathroom is the Saniflo 023 Sanicompact self-contained toilet.

Its dimensions are:

  • Depth: 21.5 inches
  • Width: 14.5 inches
  • Height: 18.5 inches

This toilet can be installed in a basement as well as bathroom far from from sewer line. Apart from being a tankless toilet, it is both an upflush as well as rear outlet toilet.

It can installed up to 9 feet below a sewer line or up to 120 feet away from a sewer line. You can also add a sink and link its gray water to the toilet output system.

What makes this toilet even better is that you don’t need floor drainage system. It makes it very easy to add a bathroom just about anywhere.

To compare this toilet with other great tankless toilets check out this post that I wrote some times back.


Tankless toilets have in the past been more popular with public toilets than in homes. Technological advancements have seen these toilets start to become a favorite for most people because of the convenience and comfort associated with them.

If you can afford to buy one then by all means go for it. These are the future toilets.