The Evolution Of The Low-Flow Toilet

Evolution Of Low Flow Toilet

Evolution of toilets

If you’re in the market for a new toilet, chances are you’ve noticed the gallons per flush rating on the toilets you’ve researched. Some of those numbers are quite small when you think about it. Only 1.28 gallons to flush an entire toilet? How is that possible? You may wonder if these toilets really work or if you’ll end up regretting your decision to purchase a low-flow toilet. Here is a look at the evolution of the lowflow toilet and some of the different features of toilets that can affect how well they do their job.

A Push For Water Conservation

Low-flow toilets first appeared about 25-30 years ago when government agencies saw reduced-flow toilets as a way to conserve water. At that time, it was normal for each flush to use 5 to 7 gallons of water. Given the number of toilets in the country, there was the potential for significant water savings if we could design toilets to work with less water. However, the real question was how to do it. It’s a question that remains today. Toilets continue to be tweaked, adapted and reengineered to provide the best flushing results using the least amount of water. Here’s a brief history of the toilet design evolution:

Modern Version Of High-Tank Toilet

Modern version of the high-tank toilet

  • The high tank toilet. These toilets had a separation of tank from bowl with the tank sitting significantly higher than the bowl. This was a purposeful design that allowed gravity to work with the water to maximize flushing power.
  • Larger, lower profile tanks. As toilet engineering continued to evolve, the tanks became less high, but were wider to make up for the lack of gravity. They featured a “flush elbow” between the tank and bowl and usually flushed with 7 gallons of water.
  • The close couple. Next came the toilets of the 1930s and ‘40s featuring a tank and bowl that were bolted together. They flushed with as much as 7 gallons or as little as 5 gallons. The high volume of water made these toilets powerful, but not very water efficient.
  • The 3.5-gallon toilet. In the 1990s Congress made the first real mandate on toilet efficiency that resulted in a 3.5 gallon per flush requirement. Toilet engineers (yes, there are such jobs!) went to work designing toilets that worked well with this amount of water. Some were successful, some were not. More often than not, problems arose in the factory when designs were rushed through to meet the mandate requirements. As a result, in 2003, MaP (Maximum Performance) testing was developed. This voluntary testing program helped manufacturers measure and improve toilet  performance. Today, over 80 manufacturers participate in the program and 2800 different toilets have been tested.
  • The 1.6-gallon toilets. The most recent toilets use 1.6 gallons per flush. Again, some models are better than others and real-world testing is the most useful way to determine which models work the best. Sometimes, it is not the highly-recognize brand-name toilets that work well, but rather the smaller companies with stricter quality controls. A qualified professional plumber can guide you to the best performing toilet for your needs.
  • The 1.28-gallon toilets. Although not yet widespread, the 1.28-gallon toilet is coming. These High Efficiency Toilets (HET) have already replaced the 1.6 gallon tanks in some models of some manufacturers.
  • The 1.0-gallon toilets. Believe it or not, there are some toilets available that flush with only 1.0 gallons of water. These toilets use a Pressure Assist technology to work.

How Toilets Can Work With Much Less Water

Viper From Geber

Illustration courtesy Gerber

The toilet’s evolution has led to better understanding of how to maximize a its function while minimizing the water used. It has also resulted in development of a few new features that aid a toilet’s task of moving waste from the bowl to the pipes.

  • Pressure-assist toilets. using Flushmate® combine gravity and compressed air to assist in flushing power. Originally used in commercial settings, these powerflush toilets have been adapted for residential use and have proven to be very successful. Pressure Assist toilets are currently available in 1.6 GPF, 1.28 GPF, and 1.0 GPF models.
  • Dual-flush models give users the option of how much water to use with each flush. Lower flow, or less water, is used for liquids, while high flow is used for solids. This has the benefit of using less water most of the time but providing extra force when needed.

    Ultra Flush From Geber

    Illustrations courtesy Gerber

Conservation will continue to drive the evolution of toilet, and with good reason. While using high efficiency washing machines is one of many techniques used for saving water, improved toilet efficiency may be one of the most effective ways to reduce your home’s water usage. Installing a new low-flow toilet can lower your water bill and help conserve water at the same time. And you can rest assured that as technology advances, so too will the toilet, and its capacity to get the job done.


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