South Dakota Water Quality Report 2026
South Dakota tap water is safe — softener may help based on our analysis of 3 water systems serving 295,544 residents. The average PurityMap score is 77.0/100 (Grade: C), which is 0.9 points below the national average.
- 2 cities (67%) have hard or very hard water (7+ GPG) which causes scale buildup and appliance damage.
- 2 cities exceed the EPA secondary TDS guideline of 500 ppm, which affects taste and may indicate elevated minerals.
- 2 cities use chloramine or have elevated chlorine residuals. Standard Brita pitchers do not remove chloramine.
A water softener is the most impactful investment for South Dakota residents in hard water areas. A basic carbon pitcher or faucet filter removes chlorine and improves taste.
Very Hard
South Dakota is 0.9 points below the US average of 77.9/100. Hardness is 6.8 GPG above the US average of 6.3 GPG.
Cities ranked by lowest score. Click any city for the full report and filter recommendations.
| Rank | City | Score | Hardness | Lead | Key Issues |
|---|---|---|---|---|---|
| 1 | Sioux Falls | 73/100 | 15.5 GPG | 2.5 ppb | Very Hard (15.5 GPG), TDS (535 ppm) |
| 2 | Aberdeen | 73/100 | 18.5 GPG | 2.0 ppb | Very Hard (18.5 GPG), TDS (650 ppm) |
| 3 | Rapid City | 85/100 | 5.2 GPG | 1.5 ppb | Hardness 5.2 GPG |
How South Dakota's 3 cities score on the PurityMap 0–100 scale:
Water quality for the most populated cities. Click any city for details.
| City | Population | Score | Hardness | Key Issues |
|---|---|---|---|---|
| Sioux Falls | 193K | 73/100 | 15.5 GPG | Very Hard |
| Rapid City | 75K | 85/100 | 5.2 GPG | — |
| Aberdeen | 28K | 73/100 | 18.5 GPG | Very Hard |
2 of 3 cities (67%) in South Dakota have hard or very hard water (7+ GPG). Aberdeen has the hardest at 18.5 GPG. Cities: Aberdeen, Sioux Falls. A water softener is recommended.
Based on EPA UCMR5 data, PFAS have not been detected above advisory levels in any South Dakota cities in our database as of 2026.
All South Dakota cities have lead below 5 ppb. Average: 2.0 ppb. Individual homes with older plumbing may have higher levels.
2 cities in South Dakota have TDS above 500 ppm. Cities: Aberdeen, Sioux Falls. RO effectively reduces TDS.
Where South Dakota gets its drinking water, based on 3 water systems.
| Source Type | Cities | % of Total |
|---|---|---|
| Surface Water | 2 | 67% |
| Mixed (Ground + Surface) | 1 | 33% |
South Dakota is a hard water state (2/3 cities). A whole-house softener is the best investment.
| # | City | Pop. | Score | Hardness | Lead | PFAS | TDS |
|---|---|---|---|---|---|---|---|
| 1 | Sioux Falls | 193K | 73/100 | 15.5 GPG (Very Hard) | 2.5 ppb | ✅ No | 535 ppm |
| 2 | Aberdeen | 28K | 73/100 | 18.5 GPG (Very Hard) | 2.0 ppb | ✅ No | 650 ppm |
| 3 | Rapid City | 75K | 85/100 | 5.2 GPG (Moderate) | 1.5 ppb | ✅ No | 180 ppm |
South Dakota has 3 utilities. Major: City of Sioux Falls Water Purification Plant, Rapid City Water, City of Aberdeen Water.
Sources: Big Sioux River and Missouri River, Rapid Creek and Pactola Reservoir, Elm River and groundwater.
- EPA Safe Drinking Water Information System
- EWG Tap Water Database
- State utility Consumer Confidence Reports
- USGS regional water monitoring data
PurityMap compiles publicly available data and does not perform independent testing.
3 city water quality reports available for South Dakota.
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