Martin Drewes remembers fretting over children subsisting on “a little bit” of bottled water, while the rest was too dirty to drink. That led to his device’s unique water wheel turning non-potable water drinkable. He then teamed up with researchers and local village women along Kenya’s Isiukhu River, to test it where potable tap water isn’t taken for granted In the case of the Waver, “the main challenge is to build the pump in the community where it is used,” Müller says. Drewes estimates that it will take five years to develop a local industry in countries like Kenya. That process could use something as ubiquitous as discarded beer kegs to fashion water wheels, although some filter components, costing as much as $1,100 apiece, would still need to be shipped from Europe or elsewhere.