India, March 9 -- A day in any Delhi household begins with an act of trust: turning on the tap. Millions of people assume that the water flowing out is safe. Other than daily washing and cleaning needs, this water fills bottles for schoolchildren, goes into morning tea, and is used in the food we eat (water purifiers are still not as ubiquitous as most people think they are). But a seven-day sampling exercise conducted by Hindustan Times at 18 complaint-prone locations suggests this trust may not always be warranted. Laboratory analysis found that nearly 44% of the samples violated basic microbiological safety standards.

The sampling was conducted keeping two factors in mind: first, it targeted areas with long-standing complaints about w...