“Impact Requires Implementation: What Dispensers for Safe Water Scale-Back Can Teach Us About Monitoring” by Tony Senanayake

TL;DR Between 2022 and 2023, GiveWell and Open Philanthropy committed over $70 million to Evidence Action's Dispensers for Safe Water programme. An independent survey in 2025 found that in Uganda and Malawi the programme was reaching approximately 70% fewer people with detectable chlorine than its own monitoring had indicated (approximately 40% fewer in Kenya). This piece argues that this case-study reflects a structural gap in how sophisticated funders allocate analytical rigour: extraordinary attention is paid to whether an intervention works under controlled conditions with far less to whether its implementation is actually delivering impact. I propose six practical steps funders can take to evaluate implementation fidelity with the same seriousness they apply to academic evidence, and I believe funders have a clear responsibility to do so. Disclosure I am the CEO of Fortify Health, an organisation that has received funding from GiveWell. I also sit on the Governance and Advisory Boards of organisations that have received funding from GiveWell. This article reflects my personal opinions and not those of Fortify Health or other associated organisations. I shared a draft of this article with GiveWell and Evidence Action prior to publication. Both organisations generously shared comments and clarifications; however [...] --- First published: April 8th, 2026 Source: --- Narrated by TYPE III AUDIO .