What are the Health Benefits of a Constant Water Supply? Evidence from London, 1860-1910

What are the benefits of moving from intermittent water delivery (which limits user access to less than 24 hours per day) to constant service? To address this question, we study the transition from intermittent to constant water supply in London. Between 1871 and 1910, the proportion of London households with access to a constant water supply (24 hours a day, 7 days a week) rose from less than 20 to 100 percent. Idiosyncratic delays in the negotiation process between companies and property owners generated random variation in the timing of the transition across London districts. Exploiting this variation, we find that a one percentage point increase in a local population with access to constant service decreased deaths from waterborne diseases by as much as 0.5 percent and explains approximately a fifth of the late nineteenth century decline in waterborne disease mortality. Results are robust to the inclusion of controls for population density, concerns regarding the reporting of cause-of-death, district-specific time trends, and spatial autocorrelation. In placebo tests, we find no evidence that the extension of constant service affected mortality from non-water borne diseases or deaths from violence.