Herndon, VA vs San Juan, PR

When comparing tap water quality between Herndon, VA and San Juan, PR, Herndon currently holds a substantial 97-point lead in average WaterQ score, with a score of 97 out of 100 versus 0 for San Juan. Herndon, VA carries an A grade while San Juan, PR carries an F. A WaterQ score reflects an aggregate of EPA-reported violations, monitoring data, and compliance history across all public water systems serving each city, so a higher score generally indicates fewer recent violations and a stronger compliance record, though it does not guarantee that every tap in the city tests identically.

Herndon, VA is the larger of the two, with 68,882 more residents than San Juan. Herndon is served by 2 public water systems, compared with 1 in San Juan — a difference of 1 system. A larger number of systems often reflects a more fragmented distribution network spanning multiple utilities, suburbs, or rural service areas, while a single large utility serving a big population can benefit from economies of scale in treatment and monitoring, but may also face more complex, aging infrastructure to maintain.

For residents of either Herndon or San Juan, the most useful next step is to look up the specific water system that serves your address, since city-wide averages combine results from every system in the area. Visit the Herndon or San Juan city pages below for a breakdown of local systems, recent violations, and contaminant-specific data, or browse WaterQ's contaminants directory to learn what each measured substance means for health.