With the persistent drought in many areas and the general concern for water conservation, high-efficiency toilets have become more and more popular. As the number of gallons per flush continues to decline, concern continues amongst consumers about the quality of the flush. However, the technology behind each toilet has progressed over time to ensure a cleaner, powerful flush. Many tests are available for manufacturers to show plumbing professionals and their clients how well HETs flush the bowl cleanly with less water.

The parts of the country most afflicted by drought — notably California, Georgia and Texas — tend to be the leaders of the pack in terms of the trend toward water-saving products, particularly because these states offer generous rebates throughout the year. However, water-saving toilets also are accepted across the country based on their performance.

As the technology continues to evolve, HETs are likely to grow in popularity. One of the most common complaints about high-efficiency toilets is that the rim and bowl are not always thoroughly cleaned with each flush. Many manufacturers offer a range of HETs across many price points and styles. Each has their own way of flushing and cleaning the bowl. Older toilets relied on a basic wash-down flush that cleared the bowl of waste simply because of the high volume of water used. Today’s water-saving toilets need to incorporate smart technology to make a low-volume flush effective.

“Prior to 1994, toilets just used more mass/water to push the waste out — not much engineering needed, with more focus on materials quality,” says Lovin Saini, senior product manager for Gerber. “Now, with high-level computer modeling, better testing instruments and a greater understanding of the plumbing inside the walls and under homes — sewage lines, piping materials, etc — the industry as a whole is looking at the toilet as a critical part of an entire plumbing system, which allows for greater understanding of fluid dynamics.”

The most commonly known industry standard test of performance is known as Maximum Performance (MaP) testing. A score is assigned based on how well toilets successfully remove a specified amount of waste from the bowl in a single flush — the greater the score the better. A soybean paste having similar physical properties (density, moisture content) to human waste is used in combination with toilet paper as the test media.

Since its initial release, some changes have been made to simplify the process. Whereas the initial protocol used uncased paste, an alternative approach uses encased soybean paste media as described in the MaP test protocol. However, organizations applying to have a fixture tested are now given the option of choosing either the new encased test media or the original uncased test media.

“We experiment with soybean paste, and put it in conditions that are seen in everyday real life,” says Bill Strang, director of operations at TOTO. “Some companies case the paste in order to reuse it. This is OK for initial tests but as you can imagine, if you case it, you won’t get the same interaction with the water and bowl — friction, shape, contours — as if it was not encased. It is imperative to get a real-world replication test. With the uncased paste, we can replicate other situations such as floating, sinking and soupy miso.”

Information from the MaP testing website says more than 3,500 different fixture models — including single-flush, dual-flush, ultra-low-flush, high-efficiency, tank-type and commercial flushometer valve/bowl models — have been tested by Veritec Consulting, IAPMO Research and Testing, and other MaP-approved laboratories since December 2003.

It is important to note that the U.S. Environmental Protection Agency adopted 350g of uncased soybean paste as the minimum performance threshold for high-efficiency toilets promoted within its WaterSense program because it is the average weight of waste produced in a “sitting.” Furthermore, most water utilities currently adopting toilet replacement rebate and installation programs with HETs also are establishing their minimum performance threshold at 350g (with some set as high as 500g minimum).


The WaterSense wave

High-efficiency toilets became popular after WaterSense was introduced around 2007, says Rob Zimmerman, senior manager of sustainability for Kohler. “There were about 30 to 50 models then, now there are several thousand,” he notes. “Once the industry figured out the engineering, it boomed.”

 This certification system tells consumers and specifiers that the product will conserve water without sacrificing performance, which is important to customers, says Jean-Jacques L’Henaff, vice president of design at American Standard. “Many 1.28 gpf toilets on the market today offer better performance than the older models while using less than half as much water,” he notes. “According to an April 2015 report by research and consulting group BRG Building Solutions, 59% of residential toilets sold in 2014 were WaterSense-certified.”

To receive WaterSense certification, toilets are independently tested to verify their flush volume meets the criteria — a maximum of 1.28 gpf — and does not exceed the volume claimed by the manufacturer.

“WaterSense certification proves key products save up to 20% or more water when compared to existing high-end standards — in the case of toilets, saving 20% more water than a 1.6 gpf toilet equals 1.28 gpf,” Saini says. “Any toilet that goes through this protocol earns the right to use the label as a validation to the contractor and end-user that it meets the strict criteria.”

Designing a well-performing toilet that uses less and less water is a constant challenge all manufacturers are facing. “As water usage decreases, the details of the trapway and flush engine become more critical to promote better flow and less energy loss,” explains Russ Denney, senior product engineer at Mansfield Plumbing.

Gravity-fed energy can only do so much, agrees Zimmerman: “Technology has helped us figure out how to reduce the amount of energy lost. I would say performance-wise most homeowners wouldn’t know they are using a high-efficiency toilet.”

While the technologies vary, what truly matters is performance. “Many people tend to associate lower flow with lower flushing power, but this is not true,” says Catalina Alanís, expert brand coordinator at Porcelana Corona de México (Vortens). “Our products development department constantly searches for new technology and design advancements, such as modifications to bowl contours.”

Other tests mandated by the American Society of Mechanical Engineers for HET models include:

  • Drain line carry.This is the pipe that takes the flushed water from the toilet and carries it away to the sewer system. “Building codes may vary, but this is sloped piping and a minimum score the ASME tests to for drain line is 40 ft. of carry,” Saini adds. “This means that every toilet sold in the market under test conditions should be able to flush and push the waste out 40 ft. away from the toilet via the drain pipe to make its way to the sewage pipe.”

What happens inside the bowl or down the drain line wasn’t a concern with older toilets that flushed with 3.5 to 5 gpf, but the EPAC law of 1992 and WaterSense changed that, Strang notes. “After the decrease in water, it became ever more important to be good at creating a model that worked well,” he says. “Consumers do want to reduce with every flush, but it is critically important it works — and works every time.”

However, some toilets don’t achieve this consistently; meaning waste sits in the drain line and requires multiple future flushes to nudge it down the line and away from the home. If a toilet consistently fails to clear the line, waste can build up and clog the drain line, and cause backflow of sewage into a home, or worse, rupture the pipe.

  • Bowl-cleansing tests/fine waste removal.This is known as a “granules” test and is meant to simulate fine waste removal and overall toilet cleanliness, post-flush. ASME calls for 2,500 tiny granules — similar to crushed tire bits in football fields — to be flushed and to only leave behind 5% or less, 125 granules, as a simulation of acceptable cleanliness.
  • Surface wash testing.A critical factor in toilet performance isn’t just how much waste can be flushed; it’s also how presentable and clean the toilet is after use. “After all, no one wants to use a dirty toilet or have to work extra hard to always keep it clean,” Saini notes.

ASME calls for a line to be drawn on the inside of the bowl, 1 in. below the rim, using a wet-erase marker. The toilet is flushed, and the remaining lines (if any) are recorded in terms of overall length remaining. The total amount of marker lengths remaining cannot exceed a complete length of 2 in., with no individual segment greater than 1/2 in.

“Contractors can show users manufacturer literature describing the testing involved and that HE toilets will perform the same, if not better, than standard toilets,” says Randy Herman, vice president of operations at Monroe, Wash.-based United Plumbing. “Another option is a sample trailer or toilet to show customers how they work.”


Growth trends

Water efficiency trends across the United States are mainly driven by drought/climate conditions and water availability.

“Today, 1.28 gpf (or lower) toilets are being mandated in drought-stricken states, and are becoming the norm as contractors and plumbers are gaining confidence in the new flush technology,” Denney says. “The EPA could possibly force the transition to HETs nationwide in the next several years. That possibility is hard to judge due to the forced transition from 3.5 to 1.6 gpf in the early 1990s, which was not very well-received due to poor toilet design.”

Salvatore Pennachio, customer service manager for Niagara Conservation, says: “We have not figured out a way to make water so we have to save what we have. HETs conserve a very important natural resource. With a toilet that works great and can help the customer save on his water bill, thus creating a rapid return on investment, I do not see any reason as to why the trend would not continue.”

Saini sees the toilet industry’s continued growth as being driven by new home construction, new commercial building construction and bathroom renovation projects. Increased adoption of lower-flow 1.28 gpf models as standard requirements in more states and increased residential toilet replacements also have factored into Saini’s estimate of future growth.

“An estimated 30 million to 40 million homes built since 1980 are in a prime repair age window,” he says. “The current estimated average age of toilets in operation in residential use is anywhere from 10 to 20 years.”

Dale Benjamin, president of Madison, Wis.-based Benjamin Plumbing, not only educates his customers about high-efficiency toilets, but conducts in-house testing with the bathrooms at his offices. “I get feedback from my plumbers about how complicated they are to install and what the quality is,” he says. “I listen to what they have to say. For example, it’s important to know if the rough-in is too tight. We do a fair amount of research and align ourselves with product lines that minimize call-backs.”

He adds that with the aging infrastructure of water and sewer systems across the country, there has to be a limit to how low the flow will go.

“I believe the next wave of innovation will come in ‘dual’ water systems — potable water to lavatories and bathing fixtures, graywater to water closets,” says Ron Capilla, president of Pleasanton, Calif.-based Can-Am Plumbing.

“The future is bright within the toilet industry,” Pennachio says. “Everyone needs a toilet and many of the older toilets are still out there waiting to be replaced.”


This article was originally titled “21st-century toilet technology” in the February 2016 print edition of Plumbing & Mechanical.