Doniphan, MO vs St Louis, MO

When comparing tap water quality between Doniphan, MO and St Louis, MO, Doniphan currently holds a noticeable 7-point lead in average WaterQ score, with a score of 68 out of 100 versus 61 for St Louis. Both cities currently carry a C grade overall. 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.

St Louis, MO is the larger of the two, with 310,251 more residents than Doniphan, yet both cities are served by the same number of public water systems (3). This means the difference in population is handled by systems of different scale rather than a different count of utilities — larger systems generally serve more connections and may have more monitoring requirements under the Safe Drinking Water Act.

For residents of either Doniphan or St Louis, 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 Doniphan or St Louis 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.