Alonso Gutiérrez, one of the mechanical engineers at Gaviotas, found the solution when he was thinking about the inherent problems of piston-driven water pumps. One problem, for example, was the seal created by the water against the sides of the sleeve. To move a piston in a piston-driven water pump in order to make the enclosed water rise, you spent energy lifting it against the pressure of that seal, as well as against the weight of both the water and of the rod and piston. Instead of wasting energy by lifting a heavy piston, why not leave the piston in place within a lightweight plastic sleeve, and lift the sleeve instead? During the dry season the water table in the llanos usually dropped below the limit of conventional hand pumps, leaving disease-ridden surface streams as the only water source. But because Gutiérrez's sleeve pump didn't require applying force against atmospheric pressure, he was certain that it could pump water from a much deeper well. The sleeve would be so light that even a small child could work the pump.
When Luis Robles, another engineer, was explaining the concept of a pump handle to some children at the Gaviotas school, one of them observed that it was similar to half a seesaw. Robles then built a seesaw and attached it to a sleeve pump outside the kindergarten so that when children played on the seesaw, they also pumped water for the school. In the late 1980s, Gaviotans brought their sleeve pumps and other appropriate technology to more than 600 villages as part of the Colombian government's Agua Para Todos (Water for Everyone) program.