Here’s the low-down on low-flow toilets and how you can choose the best models.
The average U.S. household (2.64 people) equipped with low-flow toilets saves 25 gallons of water per day, or more than 9,000 gallons per year.
Photo by Matthew T. Stallbaumer
If the toilets in your home are from the mid-1990s or earlier, consider installing new ones to save big on your water bills. All new models are “low-flow” toilets — by law they can use no more than 1.6 gallons of water per flush. Prior to 1994, most toilets on the market used at least 3.5 gallons, or about 20 gallons of water per person per day — the most water used by any household appliance. What a waste! Not only did this add to your water bills, but as recent droughts and water shortages remind us, clean water is a resource we need to conserve. Low-flow toilets now save the average U.S. household (2.64 people) about 25 gallons of water per day, or more than 9,000 gallons per year (according to the book Water Use and Conservation by Amy Vickers).
But while some low-flow models work well, others do not. That’s because to comply with the federal regulations on toilets’ water use, some manufacturers initially reduced the volume of water that discharges from the tank, without also making the necessary design adjustments. New designs have improved the performance of many models, but some still do not flush thoroughly. For a list of the best of the best, see "The Best Low-flow Toilets," below.
To be an informed shopper, it helps to know the two basic kinds of toilets available on the market.
Gravity-flush toilets. These are conventional toilets for residential use that have been engineered to use less water. When you press the knob, a flush valve opens and the water in the tank drains into the bowl through rim openings and a siphon jet. The force of the water pushes the waste through the trap and down the drainpipe. While they are usually less effective at removing solid waste than pressure-assist toilets (described below), gravity-flush toilets are generally less expensive and easier to maintain, because most use standard parts.
Pressure-assist toilets. Best suited for commercial use or in homes with poor drainpipe carry, these models use the pressure of the water supply to the toilet to compress air in an inner tank. When you flush the toilet, pressurized water is forced into the bowl, blasting waste down the drainpipe. Pressure-assist toilets have a distinctive whoosh sound that’s much louder than gravity-flush toilets, but they are more effective in removing solid waste.
Finding a low-flow gravity-flush or pressure-assist toilet that performs well is now easier than ever, thanks in no small part to a guy named Bill Gauley.
Gauley publishes toilet performance results several times a year in a report that has become the industry standard for rating toilets. His reporting on toilet performance also has pushed the toilet industry to improve its products.
Gauley’s an engineer by training, and back in the mid-1990s he was curious to know how much water his new low-flow toilet actually used. Although the unit was rated at 1.6 gallons per flush, Gauley found it used a gallon more than that. Surprised by the results, he tested other so-called “water-saving” toilets and found they all used significantly more water than the amount mandated by law. Most flushed pretty poorly, too.
Sensing an opportunity, Gauley launched a new career testing and reporting on low-flow toilet performance. The firm Gauley founded more than 10 years ago — Veritec Consulting — has helped revolutionize the toilet industry. The toilets that enter the Veritec test lab all face the same technical challenge: They must prove how much human waste (simulated with extruded soybean paste) they can flush away cleanly. The threshold for acceptable performance under Veritec analysis is 250 grams of waste cleanly expelled in a single flush (almost twice the weight of an average “deposit”).
Many toilets can successfully flush that amount and much more — the toilet listed below all flushed up to 1,000 grams of waste. But a surprising number of toilets currently on the market fall significantly below the 250 gram level.
“The marketplace is really beginning to demand better performing toilets,” Gauley says. “For example, the U.S. EPA is currently initiating a water efficiency labeling program to parallel their popular Energy Star program that will require models to flush a minimum of 350 grams of waste. Right now, the best-performing 1.6 gallon toilets can eliminate 1,000 grams or more of waste cleanly in a single flush — far more than many of the older 3.5 gallon toilet models that flushed with more than twice the volume of water.”
By choosing a low-flow toilet that works well, not only will you save money on your water bills, but you will get a reliable toilet that helps conserve water.
The toilets below received the highest rating for performance in 2005, as tested by Veritec Consulting and Koeller and Co. (Download a PDF of the whole report.)
American Standard ($250–$700)
Western Pottery ($245)
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