Conserving water usually comes with a tradeoff: What you get in savings, you lose in water flow. (Exhibit A: low-flow toilets.) RainStick’s tech, however, saves 80% of water while doubling the flow. Through a retrofit of your current shower, each drop of water is captured from the drain, blasted with UV light for sterilization, then sent upward, where it again falls from the shower head. Each drop is used six times before the device switches to new water. RainStick CEO and co-founder Alisha McFetridge estimates that in a two-person home, the device annually saves “almost a swimming pool’s worth of water.”