When the first 1.6 gallons per flush (GPF) toilets were introduced and installed in homes, both gravity-tank and pressure-assisted, consumers experienced a lot of frustration with the efficiency and performance. The 1992 National Energy Policy Act mandated the 1.6 GPF toilet manufacturing standard for both gravity- and pressure-assisted toilets, but the act focused only on consumption.
"No one had put out any requirements for performance along with consumption requirements," says Paul DeBoo of Sloan Valve Co., maker of the Flushmate pressure-assisted technology that manufacturers such as American Standard, Gerber, and Kohler incorporate into their pressure-assisted models. "So some manufacturers just dropped consumption without altering performance."
Using less water without altering toilet engineering produced problems such as clogging, dirtier bowls, and the need for multiple flushes in gravity models. Pressure-assisted models were also loud, and the velocity of the flush caused the water to splash.
Manufacturers of both flush types have since learned to adjust design features and flushing systems to increase efficiency. "In order to make these things efficient," says Pete DeMarco, director of compliance engineering for American Standard, "what we have learned by using computer-aided design is to look at the entire toilet as a system and use the energy that is provided in a specific way. In a gravity toilet, all you have to work with is the gravity pressure."
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