As part of a program to evaluate single control measures for reducing the transmission of S. mansoni, household water supplies were installed in 5 rural settlements in the Riche Fond Valley of St Lucia, W Indies. About 2000 persons previously dependent on rivers and streams now receive safe water at their homes. The systems provide useful design data on individual water requirements in rural areas. Future rural water systems can be designed more economically and efficiently by using consumption rates closer to the actual requirements and by eliminating water wastage at the taps.