Oasense's Reva showerhead goes low-flow only when no one is under it

Water-saving showerheads have a bad reputation, despite good design keeping pressure high even as less water comes out. 'Many times, people think saving water means a compromised experience, and that's something we're trying to change,' says Chih-Wei Tang, CEO of Oasense, the startup that designed the smart showerhead called Reva.

Reva's trick is that it is only low-flow when you are not under it. Before you step in, or when you are soaping up, the shower automatically slows down; as soon as you step forward, it dials up the pressure. Since as much as half the time in a shower is not spent rinsing, stepping back slightly cuts the flow to 15% of usual — and each shower can cut total water use in half.

Getting there took the designers, who started the project in a Silicon Valley garage, through 41 iterations. Knowing when a person is under the shower is hard in a steamy, foggy room, so the head needed powerful sensors — and getting power to them was solved with microturbines that let the flow of water run the device. For a family of four in California, Oasense says that can save 1,000 gallons of water a month plus the energy to heat it, around $250 a year in utilities.

The compromise was moved out of the user's way: flow drops only when no one is under the head, so the user never feels the cut.

Presence detection in a fogged-up room is the hard part, and the team iterated 41 times until the sensors were powerful enough to get it right.

Microturbines make the device self-powered by the water stream — no wiring or batteries to install, so it stays a drop-in showerhead.

The savings pitch runs on arithmetic — 1,000 gallons a month and $250 a year for a family of four in California — while the American West endures its worst drought in 1,200 years.

Efficiency features fail when they tax the user at the moment of use. The fix is to spend the savings only when nobody is looking — automate the compromise so the experience never feels compromised.

Tang argues the technology should be a de facto solution for all showerheads in the future, and that the whole shower industry should move toward smarter tech; the showerhead was featured in Fast Company's 2022 World Changing Ideas coverage.