This paper explores the impact that a water supply and sewerage (W&S) expansion had on child mortality in Quito, Ecuador. Studies have typically estimated the effects of this type of interventions comparing outcome indicators -at the aggregate level- of areas with the facilities and areas that lack them, quite often neglecting systematic differences between treated and non-treated areas. Moreover, at aggregate levels, on the one hand, less comprehensive information may imply greater unobserved and uncontrolled heterogeneity; on the other, heterogeneity within areas may jeopardize identification of impacts. To account for these key observations, we used propensity score matching (PSM) analysis at the individual level. Using indirect methods based on census data we constructed a mortality index at the motherhood level, and calculated five different impact estimators based on the propensity scores. We found that the average impact of the program ranged from 7.2 percent (local linear regression-kernel matching) to 9.0 percent (5-nearest neighbors matching). Matching difference-in-differences estimators also evidenced about an 8 percent reduction in child mortality levels. The reflexive or naïve evaluation for the cross-section would have estimated an average impact of 16.5 percent and the difference- indifferences naïve evaluation would have estimated an average impact of 19 percent, both clearly overstating the intervention's effects. When exploring heterogeneity of impacts, we stratified the sample by quartiles based on expenditure per capita, and surprisingly, no significant improvement among those in the bottom quartile was evidenced in relation to their matched individuals. However, we also observed that even in the poorest quartiles, if a woman had at least primary education, then the household obtained significant gains from W&S interventions. This would suggest the interesting observation that the overall insignificant effect for the bottom quartile was driven by the absence of impact in those who completely lacked education, thus stressing the importance of complimentary private inputs in order to reap the benefits of piped water, as other studies have suggested.