pH
Physical · measured in pH units
A measure of how acidic or basic water is. It isn't a pollutant itself, but water far outside the neutral range can be corrosive or indicate contamination.
Common sources
Local geology, acid mine drainage, industrial discharge, and — at the tap — corrosive plumbing interactions.
Health risks
Water outside the recommended 6.5-8.5 range is not usually directly hazardous to drink, but low pH ('acidic' or 'corrosive') water leaches lead and copper out of household plumbing, indirectly raising exposure to those metals. High pH reduces the effectiveness of chlorine disinfection.
Sources & further reading
- EPA — Secondary Drinking Water Standards
- CDC — Water-related Chemicals and Disinfectants
How ClearDive rates severity
Readings are bucketed for map color-coding using thresholds referenced from EPA regulatory limits where available. This is a simplified public-awareness scale, not a substitute for certified lab analysis.
How to test for it
pH test strips give a quick field estimate; a digital pH meter is more precise and easy to calibrate.