Besides, notes Cairns, president of A.H.C. Mechanical Contractors, he hasn’t had a callback on a 1.6-gpf toilet in 10 years.

How Low Can They Go?
The choice may not be optional for long. California, for example, will require all new toilets to be HETs by 2014. The Golden State has repeatedly proven itself as a standard-setter for the rest of the nation when it comes to green building legislation, and this may not be any different.

Manufacturers can comply by reducing water use to 1.28 gpf or by introducing dual-flush toilets, which feature separate flushing options for disposing of liquid and solid waste. On most dual-flush models, the liquid flush uses just 0.8 gallon, while the solid removal uses 1.6 gallons. Because users dispose of liquids three times more often than solids, water use for a dual-flush toilet averages out at 1.28 gallons per flush, so they meet WaterSense and California standards.

A few toilet makers have whittled water use even lower. Kohler’s one-piece San Raphael Pressure Lite toilet, for example, consumes just 1 gallon for every flush and can save a four-person household up to 20,000 gallons of water a year over pre-low-flush models, the company says.

That might be as low as they can go. After waste leaves the toilet bowl, it has to push through a drain line for 60 feet or so until it reaches the sewer system. Ultra-low-water toilets might have trouble “kicking it to the curb,” says James Walsh, American Standard’s product director for Chinaware.

But there are other means of lowering water consumption in the new American bathroom beyond simply using new toilet technologies. Capturing increasing attention are urinals, which can use as little as an eighth of a gallon of water per use. These are familiar and convenient fixtures in public men’s rooms—and are slowly finding their way into homes as their designs become more pleasing to women, manufacturers say.