Copper in South Dakota Drinking Water
Ranked by 90th percentile copper level (mg/L) · Data from EPA SDWIS & UCMR
Copper in South Dakota: what the data shows
South Dakota has 37 cities with copper monitoring data. The state average 90th percentile copper level is 2.095 mg/L, compared to 28.808 mg/L nationally — better than the national average. 37 cities exceed the EPA action level of 1.3 mg/L. Copper in drinking water typically comes from corrosion of copper pipes and plumbing fixtures, particularly in older homes. The EPA action level of 1.3 mg/L is the 90th percentile threshold — if more than 10% of tap samples exceed it, utilities must take corrective action including adjusting water chemistry to reduce corrosivity. Short-term copper exposure above the action level can cause gastrointestinal distress. Long-term exposure at elevated levels is associated with liver and kidney damage. Flushing your tap for 30 seconds before use and using an NSF 53-certified filter can reduce copper exposure.
Cities exceeding 1.3 mg/L EPA Action Level
Copper data across South Dakota
Each dot is a city, colored by overall water quality grade. Cities with copper levels above the 1.3 mg/L EPA action level are highlighted. Size reflects population served.
Top 10 cities by copper level in South Dakota
Highest Copper levels (mg/L)
All South Dakota cities ranked by copper level
| # | City | Level | Level | Exceeds? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Dakota Dunes | 7.600 mg/L | Yes | 0 | A- | |
| 2 | Rapid City | 4.000 mg/L | Yes | 349 | F | |
| 3 | Piedmont | 4.000 mg/L | Yes | 171 | F | |
| 4 | Viborg | 3.500 mg/L | Yes | 6 | B+ | |
| 5 | Pine Ridge | 3.095 mg/L | Yes | 138 | F | |
| 6 | Aberdeen | 3.000 mg/L | Yes | 197 | F | |
| 7 | Flandreau | 3.000 mg/L | Yes | 19 | C | |
| 8 | Fort Pierre | 2.000 mg/L | Yes | 5 | B+ | |
| 9 | Eureka | 2.000 mg/L | Yes | 4 | B | |
| 10 | Castlewood | 2.000 mg/L | Yes | 4 | A- | |
| 11 | Selby | 2.000 mg/L | Yes | 5 | B | |
| 12 | Canistota | 2.000 mg/L | Yes | 1 | A- | |
| 13 | Pierre | 1.920 mg/L | Yes | 8 | A- | |
| 14 | Gayville | 1.920 mg/L | Yes | 11 | B- | |
| 15 | Emery | 1.830 mg/L | Yes | 0 | A- | |
| 16 | Lake Preston | 1.800 mg/L | Yes | 4 | B | |
| 17 | Arlington | 1.760 mg/L | Yes | 5 | C | |
| 18 | Britton | 1.760 mg/L | Yes | 37 | C | |
| 19 | Rosebud | 1.750 mg/L | Yes | 18 | F | |
| 20 | Sioux Falls | 1.680 mg/L | Yes | 30 | C- | |
| 21 | Parker | 1.680 mg/L | Yes | 3 | A- | |
| 22 | Alexandria | 1.640 mg/L | Yes | 3 | B | |
| 23 | Volga | 1.620 mg/L | Yes | 0 | A | |
| 24 | Stephan | 1.520 mg/L | Yes | 1 | B+ | |
| 25 | Custer | 1.500 mg/L | Yes | 0 | A | |
| 26 | Brandon | 1.470 mg/L | Yes | 0 | A- | |
| 27 | Emery | 1.450 mg/L | Yes | 2 | B+ | |
| 28 | Marion | 1.450 mg/L | Yes | 0 | A- | |
| 29 | Rapid City | 1.440 mg/L | Yes | 18 | C- | |
| 30 | Salem | 1.410 mg/L | Yes | 5 | A | |
| 31 | Brookings | 1.400 mg/L | Yes | 11 | D | |
| 32 | Milbank | 1.400 mg/L | Yes | 0 | B+ | |
| 33 | Clark | 1.400 mg/L | Yes | 2 | A- | |
| 34 | Clark | 1.400 mg/L | Yes | 3 | B+ | |
| 35 | Garretson | 1.380 mg/L | Yes | 54 | B+ | |
| 36 | Hill City | 1.380 mg/L | Yes | 4 | A- | |
| 37 | Egan | 1.360 mg/L | Yes | 11 | B+ |
Frequently asked questions about copper in South Dakota
Is copper in South Dakota drinking water safe?
37 cities in South Dakota exceed the EPA action level of 1.3 mg/L for copper. The state average is 2.095 mg/L. Copper levels are highest in homes with copper plumbing, particularly when water sits in pipes overnight. Flushing the tap before use significantly reduces copper in drinking water.
What causes high copper levels in South Dakota tap water?
Copper typically leaches from copper pipes and brass fittings within homes, not from the water source itself. Corrosive (low pH or soft) water accelerates this leaching. Water utilities with high copper readings are required to adjust water chemistry to reduce corrosivity. You can reduce exposure by flushing your tap for 30 seconds before use.