This article details the rationale for the Water Equity in the Lifescape and Landscape Study (WELLS), which was carried out in the Philippines and Vietnam. Household water security is defined in terms of quantity, quality and access. The Household Water Security Mapping Tool (HWSMT) is explained in detail. The HWSMT is a rapid, participatory and relatively precise assessment tool of household level water security that is visual in nature. It is comparable among water user groups, allowing the identification of any inequities, and provides an opportunity to create a better picture of water scarcity that better reflects local realities. The strengths and limitations of the tool are briefly discussed. The article concludes by looking at the lessons learned and policy recommendations arising from the study.