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Low Flow Toilet Functioning– Explained by Specialists

how do low flow toilets work
Written by Kai Michel
Last Update: August 10, 2023

Low-flush or low-flow toilets are very popular with many house owners who want to store water, save money, or reduce their home’s environmental impact. These effective, water-saving toilets have gone a long way since their first introduction in the 1990s, with many models commercially available, providing better performance and more choices than in past years.

Although low-flow toilets are much more costly to install and maintain than their conventional counterparts, they will also save you a considerable amount of money in the long term.

How Do Low Flow Toilets Work?

How Do Low Flow Toilets Work

Modern flow toilets are far more reliable and economical, and their components are also more compact and easy to replace. Flow toilets, often also named low-flow toilets, typically use one of two principles for removing waste: pressure-assisted or gravity method. Nevertheless, both toilets use around 1,6 gallons (6 liters) of water per flush or even less.

Gravity toilets remove waste once the flapper is pushed, and water is emitted, dropped from the reservoir, and flushed through the bowl. Gravity pushes waste away from the bowl. Pressure-assisted toilets, on the other hand, compress a bubble of air that serves to stimulate the water released after each splash into the bowl.

Pressure-assisted toilets are somewhat noisier than gravity-fed variants and are typically more expensive, beginning at $150 instead of $75 for gravity-fed types. Below is a detailed description of how does a flow toilet work explained on two major types of low-flow toilets.

1. Working Principle of Gravity-Fed Low-Flow Toilets

Although pressure-assisted toilets have become more common, the traditional gravity-fed configuration of toilets in residential homes still remains the most popular choice. Once the toilet lever is pulled, the flush mechanism inside the reservoir connected to a lift chain raises a flapper mechanism at the bottom of the container; enabling a large volume of water to flow down from the reservoir and through the splash valve opening inside the toilet bowl.

Water’s powerful movement drives waste from the toilet bowl via the toilet pit and then through the building drainage system into the public sewage lines or septic area. While the water goes down the bowl from the reservoir, it passes through several openings at the bottom and establishes a circular movement of the water in the bowl that helps to wash the waste out from it.

When the water level increases in the reservoir, the float sphere or float ball rises alongside the water. When the water hits the appropriate level the filling mechanism shuts off, and the toilet ends up “working.” After that, the gravity toilet is ready for next use. Gravity-fed toilets are by far the most common and economical solutions because they are inexpensive and efficient. In principle, gravity toilets are still more than adequate to satisfy the needs of most residential and commercial environments, but in terms of pure effectiveness can be less than ideal than pressure-assisted variations.

2. Working Principle of Pressure-Assisted Low-Flow Toilets

Pressure-assisted toilets appear like ordinary toilets supported by gravity before you look within the reservoir. There is just a closed, plastic pressure container in place of a tank of water. There are air and water within the container. While the reservoir is filling with water during a refill process, the air in the container will be under the pressure of the water system in the house.

After the toilet is flushed, the reservoir releases the water under pressure, which creates a heavy burst of water into the bowl. Once the water is drained, the container refills with air. After the flush, a filling valve activates automatically, as with normal toilets, to fill the reservoir with water.

The pressure-assisted model provides a better water flow, which cleans the bowl quicker, eliminates waste better, and washes more thoroughly than a traditional gravity-fed mechanism. Compared to some calculations, pressure-assisted toilets will also flush 50 percent further than gravity toilets, leading to cleaner drainage pipes and less risk of clogging along the road. Another main advantage of the toilets aided by pressure is water conservation. Pressure-assisted toilets can use around 15 to 35 percent less water when compared to typical modern toilets.

The main disadvantage of toilets assisted by pressure can be summarized in two words: noisy flush. Another downside of pressure-assisted toilets is their complex structure. They have more components and operational aspects than gravity toilets, so this implies more potential complications and problems.


Low flow toilets conserve huge amounts of water, both through the splash and over time. Whether you are installing a model that supports gravity or pressure, a low-flow toilet will considerably reduce water consumption needed to stream waste through the drainage system and away from home. If interested in implementing water-saving installations at home, you’ll be pleased to learn that converting from a conventional model to a low-flow toilet could save you around $200 per year.


1. What Makes a Toilet Low Flow?

Ans. Since 1992, the United States government has specified that new toilets produced in the United States have to be low-flush or low-flow, which implies that they use no more than 6 liters (1.6 gallons) of water per flush.

2. Does Putting a Brick in the Toilet Tank Save Water?

Ans. Adding a concrete block in the toilet could save a tiny amount per splash, as the brick reduces the reservoir capacity, but this can significantly affect toilet efficiency.

3. How Much Water Do Low Flow Toilets Use?

Ans. While toilets all appear much the same, the amount of water generated by flushing varies greatly between toilets. Usually, older toilets will use more water. Toilets built before 1982 consume 5 to 8 gallons of water per flush. Toilets are now constructed to flush with just 1.6 gallons.

4. Why Are Low Flow Toilets Good for the Environment?

Ans. Besides saving income on water, you can also help protect local water supplies by choosing a low flow toilet. Low flow toilets have been designed to avoid large quantities of water being extracted from the municipal pipes.

About the author

Kai Michel

Hello, this is Kai, addressing homeowners in need of some help with their home renovation projects. I’ve worked on numerous toilet repair projects over the years that incorporated a wide variety of tasks, from repair to renovation and maintenance. Besides acquiring a degree on the legal codes and procedures, I gathered vast insights into bathroom settings, toilets, showers, fittings, and other household appliances, fixtures, and components. This helps me guide my clients through their home improvement and interior development plans. Since maintenance is my area of expertise, I can assist people in all phases of the actual ‘improvement’ process. To get my messages even further, I contribute to this site through my blog posts. Check my content here for expert suggestions!

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