A few years ago, an engineer was taking a shower and started looking at the water going down the drain and wondering how much energy was going with it. The answer, it turned out, was pretty large: after heating and cooling, hot water uses more energy than anything else in the typical home, and 80-90% of that energy is wasted seconds after the water flows out of the showerhead.
What if the heat could be recaptured to keep the shower hot? After working with a team on 4,700 different experiments and iterations, engineer David Velan had a new design that worked—a device that pulls heat from water as it flows out and transfers it back into the clean water to warm it up. Since the product is double-walled, the dirty water is fully separated; only the heat is transferred, helping recover about 45% of the energy that would have otherwise gone down the drain.
It wasn't the first time that someone had tried do something similar, but it might be the first to do it in a way that's really practical. "Recapturing heat from shower water is deceptively simple," says Velan. The device had to be easy to install in different settings, cost effective, long lasting, and safe. "It is relatively easy to meet a couple of these criteria at a time, but difficult to hit them all," he says. "We have had to build hundreds of physical prototypes."
The EcoDrain is horizontal, so it's easy to install next to the drain where the water is the hottest. The designers estimate that it can pay for itself in two years if you have expensive electricity, and then last for up to 30 years. For places that use even more hot water—like laundromats, hotels, and gyms—the energy savings are even greater.
At a hospital, where the device is installed on a large laundry machine that runs most of the day, Velan estimates that it has 768 times more energy and cost saving potential than it does used in a single 10 minute shower.
It can also be used in more unexpected ways. "Cool drain water, such as from the toilets in an office building can be used to provide free cooling," says Velan, explaining that one of the earliest forms of air conditioning used fresh water in a heat exchanger. It wasted water, but if it can capture cool water that's already going down the drain, that's yet another way to save energy.