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    Clean water

    Clean water: A safe glass of water, for everyone.

    Unsafe water still makes children sick and takes young lives. Treating it costs little. The honest hard part is making sure people drink it.

    Try it in the sliderTalk to Ryan

    Ryan K. Hertel · heyitskenton

    The problem

    What we're up against.

    • Too many still go without.

      2.1 billion people still lack safely managed drinking water, and 106 million drink straight from untreated surface water, like rivers and ponds.

    • Contaminated at the source.

      In 2022, at least 1.7 billion people drank from a source contaminated with faeces. Contaminated water causes an estimated 505,000 deaths from diarrhea a year.

    • Children pay the most.

      Diarrhea kills around 443,832 children under five every year.

    What works

    Proven, and ready to grow.

    • Treated water saves children's lives.

      Pooling 18 trials, a meta-analysis found that treating water cut the odds of young children dying, from any cause, by 24% to 27%.

    • Even the cautious estimate is real.

      GiveWell's own re-analysis is more careful: about 14% fewer child deaths pooled across trials, and 6% to 11% for two chlorination programs after its adjustments.

    • Chlorine in the pipes, no effort needed.

      In-line chlorination doses water as it flows. In a double-blind trial in Dhaka, water at the taps carried chlorine 83% of the time, and in rural India it cut E. coli in tap water by 70%.

    • Fewer sick children.

      Across trials, giving families chlorine to treat water at home may cut diarrhea by around one quarter.

    What a family could fund

    Where the money goes furthest.

    • Chlorine where people collect water.

      Evidence Action's chlorine dispensers and in-line chlorination cost less than $1.70 a person a year, and it says nearly 10 million people have safe water through its work.

    • Room to grow in Africa.

      GiveWell has backed pilots of in-line chlorination in six African countries, around $16 million in grants, and estimates there could be more than $100 million in highly cost-effective work to follow.

    • Making government water safe.

      In India, chlorinating government piped water costs about $1 to $3 for each extra person-year of coverage, by GiveWell's estimate, with the government bearing a large share of the costs.

    • A gap other funders leave.

      GiveWell is one of only a few funders of last-mile chlorination; other donors are generally more focused on access.

    Honest limits

    What money can't promise.

    • Access isn't use.

      Surveys found about 2 million people using the dispensers, not the 5 million estimated, and Evidence Action is winding the program down in Malawi.

    • The size of the effect is uncertain.

      Around its pooled estimate, GiveWell's range runs from a 32% drop in child deaths to a 10% rise. Honest counting means paying for the studies, too.

    • Chlorine doesn't stop every germ.

      It does little against Cryptosporidium, a common cause of diarrhea in children in low-income places.

    • Pumps and pipes break.

      At any time, about one in four handpumps in sub-Saharan Africa don't work.

    Hard questions

    Asked and answered.

    1. You might ask

      Do people actually use it?

      Ryan

      In trials, yes: take-up of free dispensers stayed over 50% two years on, while fewer than 10% of households regularly used chlorine they had to buy. At scale, fewer used them than claimed, which is why chlorine in the pipes, which asks nothing of anyone, matters. In rural India, people kept drinking the piped water even when they noticed the taste.

    2. You might ask

      Doesn't infrastructure break down?

      Ryan

      Often: about one in four handpumps in sub-Saharan Africa don't work at any given time. GiveWell calls in-line chlorination challenging, because every water system differs. So the money has to pay for upkeep and independent checks, not just installation.

    3. You might ask

      Isn't this the government's job?

      Ryan

      The best work helps governments make their own water safe: in India, the government bears a large share of the chlorination program's costs. Other donors are generally more focused on access, which leaves water quality as the gap a family can fill.

    In the slider

    See what your fortune could do here.

    Clean water

    The slider prices this cause with these numbers:

    • Less than $1.70 a person a year gives access to chlorinated water at shared water points.
    • The whole need is everyone without safely managed drinking water, 2.1 billion people.
    • Access isn't use: a later survey found about 2 million people using the dispensers, not the 5 million estimated.
    Try it in the sliderTalk to Ryan

    More of the Blueprint

    Keep reading.

    23 more chapters on the way

    Back to Keep 100

    Sources

    Every number in this chapter, and where it came from.

    1. Source 1: Diarrhoeal disease: fact sheet (opens in a new tab)

      World Health Organization, 7 March 2024. Checked 16 October 2026.

    2. Source 2: Following the data on Dispensers for Safe Water (podcast episode 25) (opens in a new tab)

      GiveWell, 5 March 2026. Checked 15 October 2026.

      A survey in Uganda and Malawi.

    3. Source 3: Progress on household drinking water, sanitation and hygiene 2000-2024 (opens in a new tab)

      WHO and UNICEF Joint Monitoring Programme, August 2025. Checked 15 October 2026.

      Safely managed means water at home, available when needed and free from contamination.

    4. Source 4: Drinking-water: fact sheet (opens in a new tab)

      World Health Organization, 13 September 2023. Checked 16 October 2026.

    5. Source 5: Water Treatment And Child Mortality: A Meta-Analysis And Cost-effectiveness Analysis (Kremer, Luby, Maertens, Tan and Wiecek) (opens in a new tab)

      National Bureau of Economic Research, February 2026. Checked 16 October 2026.

      A working paper, first issued in January 2023 and revised in February 2026; not yet published in a journal.

    6. Source 6: Water Quality Interventions (opens in a new tab)

      GiveWell, April 2022. Checked 16 October 2026.

      GiveWell's own re-analysis of the trials, more cautious than the meta-analysis.

    7. Source 7: Effect of in-line drinking water chlorination at the point of collection on child diarrhoea in urban Bangladesh: a double-blind, cluster-randomised controlled trial (Pickering and others) (opens in a new tab)

      The Lancet Global Health, September 2019. Checked 16 October 2026.

      A randomized trial at shared water points in Dhaka.

    8. Source 8: In-line chlorination for drinking water in rural Odisha, India: A randomized controlled implementation trial (Lowe and others) (opens in a new tab)

      PLOS Water, 29 April 2026. Checked 16 October 2026.

      A randomized trial in 20 villages.

    9. Source 9: Interventions to improve water quality for preventing diarrhoea (Clasen and others) (opens in a new tab)

      Cochrane, 20 October 2015. Checked 16 October 2026.

      A systematic review; the evidence for chlorine at home is rated low quality.

    10. Source 10: Safe Water Now (opens in a new tab)

      Evidence Action. Checked 15 October 2026.

      Chlorine dispensers and in-line chlorination at shared water points. The figure counts people given access.

    11. Source 11: Safe Water Projects: Saving Lives and Improving Our Grantmaking (opens in a new tab)

      GiveWell, 29 October 2025. Checked 16 October 2026.

    12. Source 12: Evidence Action: Scale-Up of In-Line Chlorination in India (September 2023) (opens in a new tab)

      GiveWell, April 2024. Checked 16 October 2026.

      GiveWell's estimate for a grant, before results were in.

    13. Source 13: Research Strategy: Water (opens in a new tab)

      GiveWell, 26 June 2024. Checked 16 October 2026.

    14. Source 14: Functionality of handpump water supplies: a review of data from sub-Saharan Africa and the Asia-Pacific region (Foster, Furey, Banks and Willetts) (opens in a new tab)

      International Journal of Water Resources Development, 2020. Checked 16 October 2026.

      A review of data from many countries, via the authors' university repository.

    15. Source 15: Chlorine Dispensers for Safe Water in Kenya (opens in a new tab)

      Innovations for Poverty Action. Checked 16 October 2026.

      A summary of randomized studies in Kenya.