How Low Can You Flow? How to Create an Energy-Efficient Bathroom

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Every day, water and heat disappear down the drain in your bathroom, making this room the first place to look for cutting costs and resource use. Starting with faucet aerators, low-flow showerheads, and low-flush toilets, a plan for resource efficiency in bathrooms might also include composting toilets, micro-flush toilets, dual-flush toilets, and even systems irrigated with graywater.

For a look at just how far you can go—should you have the desire and the means—step inside Diane Cotman’s turn-of-the-century home in Cambridge, Massachusetts. In one bathroom, a trim white SeaLand Traveler toilet flushes with just one pint of water via a foot-pedal on the side. The toilet drains to an EcoTech Carousel composting toilet system in the basement that processes the waste into a soil-like humus. In another bathroom, a high-tech and high-design Toto Zoe Washlet toilet provides non-clogging 1.6-gallon-flushing—as well as a built-in bidet, air dryer, and deodorizer. A stainless steel bathtub recirculates hot water through the walls of the tub, keeping bathwater warm.

Wastewater from Cotman’s sinks and tubs—called “graywater”—is filtered and drained to specially engineered planters in window alcoves in the bedrooms, where it is used to water plants such as orchids, birds of paradise, and other colorful tropical varieties. Solar collectors and a geothermal pump heat the water for the house’s sinks and tubs as well as the radiant heating and cooling system.

Cotman’s bathrooms are an extreme example, but there’s plenty to do for those seeking simpler solutions.

Toilets

A 1.6-gallon low-flush toilet can cut household water usage by 20 percent or more. Required in all new construction, low-flush toilets have come a long way since the early days, when most U.S. low-flush models were prone to double-flushing and clogging. Changes in design have produced high-performing units that can significantly reduce home water use and take a load off septic systems and municipal water supplies.

Every low-flush toilet conserves between twenty-five and sixty gallons of water per day each, saving owners an estimated $50 to $100 on annual water bills.

Recognizing that less water is needed to flush urine, new “dual-flush” toilets feature two flush buttons: Press the dark one to flush feces with 1.6 gallons of water or press the light one to flush only urine with 0.8 gallon. Caroma’s dual-flush from Australia (where this style is mandated for all new buildings) is now imported to the United States; prices start at $250.