Seeds of the plant species Strychnos potatorum and Moringa oleifera contain natural polyelectrolytes which can be used as coagulants to clarify turbid waters. In laboratory tests, direct filtration of a turbid surface water (turbidity 15–25 NTU, heterotrophic bacteria 280–500 cfu ml−1, and fecal coliforms 280–500 MPN 100 ml−1), with seeds of S. potatorum or M. oleifera as coagulant, produced a substantial improvement in its aesthetic and microbiological quality (turbidity 0.3–1.5 NTU, heterotrophic bacteria 5–20 cfu ml−1, and fecal coliforms 5–10 MPN 100 ml−1). The method appears suitable for home water treatment in rural areas of developing countries. These natural coagulants produce a ‘low risk’ water; however, additional disinfection or boiling should be practised during localised outbreaks/epidemics of enteric infections.