Its a Myth That Low-Flow Toilets Don't Work

Early Low-Flow
In the 1970s and '80s, most toilets consumed 3.5 gallons of water per flush, and some consumed as much as 5 or 7 gallons. Then came the Energy Policy Act of 1992 that mandated a maximum of 1.6 gallons (6 liters) of water per flush. (This federal law was actually modeled after a Massachusetts law that was the first in the nation to regulate flush volume.) The initial response by most toilet manufacturers was to tweak their existing models to use less water—usually by closing the flush valve more quickly after the toilet was flushed. Because the bowls and trapways of these toilets were designed to use 3.5 gallons, performance was often a problem. With restricted flow, toilets clogged or required a second flush to remove the wastes or paper, or they left the bowl streaked and needing frequent cleaning. Many consumers and their builders or remodeling contractors were not happy.

General dissatisfaction with American toilets opened up the market to products from Europe (especially Scandinavia) and Japan, where water conservation had long been a priority and manufacturers had figured out how to make low-flush toilets that worked. Manufacturers such as Ifo and Toto began making inroads into the U.S. market as U.S. manufacturers gradually woke up to the need to redesign their toilets from the ground up. Spurred by complaints about poor performance—and recognizing that the industry-accepted standard test procedures from the American Society of Mechanical Engineers (ASME) and the American National Standards Institute (ANSI) did not accurately assess flush performance in real-world applications—there were a number of efforts, starting around 2000, to test toilets more objectively. With utility funding, the NAHB Research Center put 49 popular toilets through a battery of tests and reported in 2002 that nearly three-quarters of them performed unsatisfactorily. In October 2002, Consumer Reports published an article on toilet performance that used very different testing methods and produced strikingly different results. Consumers and builders were left frustrated and without a place to turn for toilet performance information they could trust.

In response, more than a dozen municipal water utilities in the United States and Canada—including agencies that were actively promoting water conservation—funded projects to develop a comprehensive testing protocol that would accurately measure toilet flush was the Maximum Performance (MaP) testing. MaP measures how much mass of a standardized testing media (cultured soy encased in latex sleeves) a toilet will flush successfully in two out of three tries. Test media is added and the toilet is flushed in a stepwise fashion until test media is left in the toilet — the greatest mass flushed successfully is the toilet's MaP rating. Developers of the MaP test deter-mined that a minimum rating of 250 grams is required for adequate flush performance. MaP performance of toilets is also now one of the criteria we use at BuildingGreen Inc. for approving toilets into our GreenSpec® Directory.

This MaP testing approach has now been incorporated into the broader voluntary Uniform North American Requirements (UNAR) for Toilet Fixtures, which is likely to become the de facto standard for toilet performance—superseding the code-based ASME/ANSI performance standards.

What's New with Toilets?
Along with the MaP testing and the UNAR program, there have been dramatic developments with toilets in the past few years.

Pressure-assist toilets. When performance problems occurred with conventional gravity-flush toilets, some manufacturers turned to pressure-assist technology to boost performance. In a pressure-assist toilet, as the tank refills after flushing, the water compresses air in a specialized pressure tank inside the vitreous china tank. During flushing, the compressed air results in a higher-velocity flush, which very effectively removes solids. Pressure-assist toilets tend to be noisier (with a startling whoosh) but newer models are somewhat quieter, and several lower-volume pressure-assist flush systems have recently been introduced.

High-efficiency toilets. High-efficiency toilets (HETs) use at least 20% less water than the 1.6 gallons per flush (gpf) standard. Thus, the threshold for HETs is 1.28 gallons or 4.8 liters. Water conservation programs in six states (CA, CO, FL, NM, TX, and WA) are currently offering rebates for HETs. A 1.28-gpf toilet will save a typical family 4,000 gallons of water per year.

Dual-flush toilets. Dual-flush toilets offer two flush-volumes: a full-volume flush (1.6 gallons) for solids and a water-saving flush (0.8 to 1.1 gallons) for liquids and paper. There are now at least a dozen dual-flush toilets on the market in the United States. A dual-flush toilet using 0.9 gallons for the low-volume flush should save a typical family about 7,000 gallons of water per year.

Credit: Alex Wilson, Green Builder

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