It is common to argue that water infrastructure innovations improve life expectancy. Yet the benefits of clean water depend on a mechanism to dispose of waste water. We draw on the historical experience of a large industrial city to estimate the impact of the spread of the sewer system. Using a longitudinal data set on mortality and rents for each of Paris’ 80 neighborhoods we show that sanitation contributed several years to life expectancy. These results point out the multiplicity of infrastructure needed to help decrease mortality.