In the US, there are roughly 150,000 public water systems (PWS) that serve people for at least 60 days a year. Community water systems (CWS) serve the same population as PWS but over the course of a year. Non community systems serve places such as restaurants. CWS serves about 95% of the population in the US. Although this accounts for most Americans, CWS are not evenly distributed across service-sized populations.

Contrary to what you might think, the WHO does not actually recommend a uniform international enforceable standard for drinking. With the increasing amount of industrial activity humans are engaging in, this has made contamination in water a more important issue than in years past.

References

https://www.nature.com/articles/s41370-023-00597-z

https://www.sciencedirect.com/science/article/pii/S2667325826000117