Awareness of water’s value, high water losses, occasional water shortages and increased costs arising from new treatment requirements has increased focus on reducing water losses. For water loss management, SELL (sustainable economic level of leakage), can be used. SELL includes not only the long-term utility costs and benefits, but also external social and environmental leakage costs, including traffic disruption during pipe repair and replacement work, carbon footprints and health risk effects from leaking pipes with inadequate pressure. The aim of the project was to adapt SELL to Norwegian and Swedish conditions and prepare a calculation model for SELL for use by water utilities. A spreadsheet was developed to calculate water balances and leakage. Another was developed for calculating SELL for the utility. The latter spreadsheet includes researchbased default values if no local data are available. An uncertainty analysis was used to show how much input data uncertainty affects the result. The conclusions are that, when all externalities are included and new leak reduction techniques are developed, SELL is lower than expected. The authors believe that the manual will help significantly in fighting water losses, especially for small-and medium-scale water utilities.