Largest public system
- City of Rock Hill: Hardness
- 35 mg/L
- About 2 grains per gallon: soft by USGS classes. Average (2025).
- City of Rock Hill Utilities (hosted by York County, SC), 2025
- City of Rock Hill: Disinfectant
- Chlorine dioxide and chlorine
- City of Rock Hill Utilities (hosted by York County, SC), 2025
- City of Rock Hill: TTHM (disinfection byproducts)
- 52 ppb
- Highest running annual average (2025); federal limit 80 ppb.
- City of Rock Hill Utilities (hosted by York County, SC), 2025
- City of Rock Hill: HAA5 (disinfection byproducts)
- 37 ppb
- Highest running annual average (2025); federal limit 60 ppb.
- City of Rock Hill Utilities (hosted by York County, SC), 2025