WHO: Gary Hopkinson

WHERE: Dunstable

Gary Hopkinson A septic failure in 2003 caused Hopkinson, 61, to go green when he learned he couldn't simply replace his old system due to poorly draining soil. Instead, he was told, he'd need to install a tight-tank system, which he calculated would cost at least $14,000 annually to run. "We could never sell the property with that kind of operating overhead," says Hopkinson, who is a senior vice president at Transgas. For alternatives, he turned to David Del Porto at Ecological Engineering Group, a Weston company that researches, designs, and installs eco-friendly wastewater treatment systems. The solution, called Ecocyclet, runs blackwater (toilet waste) to a holding tank for disposal, and graywater fluid (from sinks, dishwashers, baths, and washing machines) to a year-round, 22-by-30-square-foot greenhouse on the property. There, native and tropical plants soak up the water, eventually releasing clean vapor into the air. (Hopkinson and his family protect the hardworking plants by using only biodegradable cleaners in their house.) The system was designed for the three-bedroom home based on very low daily water consumption. "Because we'd already used a septic system, we were used to thinking conservatively about water, but now we're even more motivated than before," he says.