NeatWork is an optimization and simulation tool for the design of purely gravity-driven water-distribution systems with the objective of delivering clean water to poor rural communities. NeatWork proposes a heuristic approach for the design of least-cost systems under stochastic intermittent water demands, in which devices, such as pumps and pressure regulators, which are operated by humans and commonly used to control pressures and flows, are excluded. The resulting designs are thus as simple and as robust as possible to operate, and the operating, maintenance, and investment costs are kept as low as possible, an important requirement in poor rural communities. We illustrate the application of NeatWork on a typical project implemented by Agua Para La Vida, the nongovernmental organization currently using the tool for its activities in Nicaragua.