Over one billion people are without access to safe water, while twice as many lack access to improved sanitation services, making these two of the world's most pressing issues. The sustainability of critical infrastructure systems, such as water and sanitation, is a necessary (though not sufficient) criterion for achieving sustainable human settlements since the lack of adequate services affects literally all aspects of a Community's daily existence including health, education, family, surroundings, and employment. Despite several decades of development aid, infrastructure solutions have not significantly improved these water and sanitation problems (with few exceptions). In this paper, we consider the holistic nature of water infrastructure development in terms of rural areas in developing countries. We propose an outcome-based evaluation method using Life-Cycle Analysis to examine three categories of infrastructure sustainability metrics: technical, environmental, and economic; both from a community perspective, and a social-equity perspective. We demonstrate the method with a simple, generic example of arsenic treatment approaches in Bangladesh.