Long before modern medicine had much to offer, clean water was already quietly doing some of the most important preventive work in public health. Many of the diseases that once spread easily through a population travel through contaminated water, which means separating drinking water from waste is a remarkably effective form of prevention.
The engineering behind it is unglamorous: pipes, treatment plants, and testing regimes that most people never think about unless something goes wrong. That invisibility is, in a strange way, a sign of success, since a well-run water system is one nobody has to notice or think twice about.
It is worth remembering how much of that protection is systemic rather than personal. No amount of individual carefulness fully replaces safe water and sanitation at a community level, which is part of why public health has always treated basic infrastructure as a foundation rather than an optional extra.