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17 cities ranked best to worst by EPA-record water quality score
Sioux Falls has the best tap water grade in South Dakota (A, 100/100); Aberdeen is lowest (F, 58/100). 2 of the 17 graded systems have a health-based EPA violation in the last five years; 88% earn a B or better, so safety depends on your utility. Statewide, South Dakota ranks #16 of 51 states for water quality (average 94/100 vs 87 nationally) — see every state's rank.
This page ranks the 17 South Dakota cities whose water systems we have matched to EPA records. Every city starts at 100 points and loses points for health-based EPA violations in the last five years (SDWIS 2026Q2), its most recent Lead and Copper Rule 90th-percentile result, PFAS detected in EPA's 2023–2026 UCMR5 monitoring, and 2012–2019 compliance samples that averaged near or above a limit. Letters follow fixed bands (A ≥90, B ≥80, C ≥70, D ≥60, F below 60). Cities run from the highest score (Sioux Falls) down to the lowest (Aberdeen); ties are ordered by population served. See the full scoring methodology for every deduction and the data vintages.
An A or B grade points to water that consistently tests within federal safety limits, while a C suggests moderate issues worth watching and a D or F flags contaminants or compliance problems serious enough to act on. These grades describe system-level water leaving the treatment plant — they can't account for your home's own plumbing, so older houses with lead service lines or fixtures can add contaminants after the water arrives. For a contaminant-by-contaminant view, see the South Dakota contaminant breakdown or drill into the county-level rankings.
What the EPA service line inventory and our South Dakota guide say, beyond the scores.
17 South Dakota cities have a report on this site. Those 2 systems report serving 288,471 people in EPA's Safe Drinking Water Information System (SDWIS).
Of all 17 cities South Dakota cities we can grade from EPA records, 15 cities (88%) grade B or better, 0 sit in the C range and 2 grade D or F. The average score is 94/100.
EPA records 14 health-based violations in the last five years across 2 cities. Monitoring and reporting violations (3 in the same window) are paperwork lapses and cost far fewer points.
17 cities have a Lead and Copper Rule 90th-percentile result from 2020 or later: 3 cities at 5 ppb or more.
EPA's UCMR5 PFAS monitoring (2023–2026) covers 17 cities: PFAS were detected in 3 cities, all below the 4 ppt PFOA/PFOS limit.
Dell Rapids scores highest (100) and Aberdeen lowest (58), a 42-point spread.
Because lead enters water after treatment, the most useful statewide number is the service line inventory South Dakota utilities filed with EPA (Q2 2026). 478 South Dakota systems inventoried 326,512 service lines: 2,081 confirmed lead plus 616 galvanized lines requiring replacement, spread across 61 systems. The bigger number is 96,462 lines (30%) whose material is still unknown — more than one line in four — and EPA treats unknown lines as possible lead until a utility verifies them.
Of the 2 city-linked South Dakota utilities with an inventory on file, 2 report at least one lead or galvanized-requiring-replacement line. The largest, SIOUX FALLS (Sioux Falls, 216,462 served), reports 15 lead lines and 21 galvanized requiring replacement. The most lead lines among city-linked systems belong to RAPID CITY (Rapid City): 106.
| Contaminant | Federal limit | Cities elevated | Over limit | Highest reading | Why it matters |
|---|---|---|---|---|---|
| Lead | EPA action level 0.015 mg/L (15 ppb); health goal 0 | 1 | 0 | Brookings | Lead harms brain development in children and raises blood pressure and kidney risk in adults. |
| PFAS | EPA 2024 MCLs of 4.0 ppt for PFOA and PFOS | 1 | 0 | Rapid City | PFAS are linked to immune, developmental, liver and some cancer effects. |
Service line counts: EPA SDWIS Service Line Inventory, Q2 2026 snapshot (updated 2026-08-18). Limits: EPA National Primary Drinking Water Regulations.
How South Dakota's 17 cities are distributed by water quality grade
15 out of 17 cities meet or exceed a B grade for water quality
Sorted by water quality score from best to worst. Click any city for a detailed water quality report.
| Rank | City | Score | Grade |
|---|---|---|---|
| 1 | Sioux Falls | 100/100 | A |
| 2 | Watertown | 100/100 | A |
| 3 | Yankton | 100/100 | A |
| #4 | Pierre | 100/100 | A |
| #5 | Spearfish | 100/100 | A |
| #6 | Dell Rapids | 100/100 | A |
| #7 | Tabor | 100/100 | A |
| #8 | Miller | 100/100 | A |
| #9 | Vermillion | 100/100 | A |
| #10 | Mitchell | 99/100 | A |
| #11 | Brandon | 98/100 | A |
| #12 | Harrisburg | 98/100 | A |
| #13 | Brookings | 97/100 | A |
| #14 | Huron | 97/100 | A |
| #15 | Rapid City | 95/100 | A |
| #16 | Box Elder | 60/100 | D |
| #17 | Aberdeen | 58/100 | F |
Sources: EPA SDWIS/ECHO violations and Lead and Copper Rule results (2026Q2 extract), UCMR5 PFAS occurrence (2023–2026), SYR4 compliance samples (2012–2019). Rubric v2 — methodology.
Found your city above? These guides turn its grade into an action plan.
Pitcher vs. under-sink vs. reverse osmosis, matched to the contaminants reported in South Dakota systems.
Taste, odor, trihalomethanes, and why a carbon filter handles them
Where it comes from, how to test, and which filters are NSF 53 certified to remove it
Best filters for lead →EPA's inventory of lead pipes by water system — a risk these plant-level grades cannot capture.
Put a South Dakota city next to where you're moving from (or to) and see every contaminant head to head.
The best water quality in South Dakota is found in Sioux Falls with a score of 100/100 and a grade of A. This puts Sioux Falls among the top-performing cities in the country for drinking water safety.
The most concerning water quality is in Aberdeen scoring 58/100 with a grade of F. Residents may want to consider home water testing and filtration options.
The statewide average score is 94/100, which is 7 points above the national average of 87/100. A strong majority (88%) of South Dakota cities exceed the national average, indicating generally good water infrastructure across the state.
2 South Dakota cities have a D or F grade. Residents in those areas — and anyone wanting extra protection — should consider a certified water filter that removes the specific contaminants found in South Dakota water systems.
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Sioux Falls has the best water quality grade among the 17 South Dakota cities we can grade, with a score of 100/100 (grade A). Scores start at 100 and lose points for health-based EPA violations, lead 90th-percentile results, PFAS detections in EPA's UCMR5 monitoring and historical (2012–2019) readings near a limit. 9 cities share this top score; the largest system is listed first.
It varies by utility. Across the 17 South Dakota cities we grade from EPA records, the average score is 94/100 and 88% earn a B or better. 2 cities have at least one health-based EPA violation in the last five years. 2 cities grade D or F; residents there should consider a certified filter matched to the finding on the city page. Lead from household plumbing is not captured by any city-level grade.
South Dakota ranks #16 of the 51 states we grade, with an average city score of 94/100 against a national average of 87/100. The state rank is the mean score of each state's graded cities from EPA records; within South Dakota, Sioux Falls ranks #1 of 17 cities.
By population served: Sioux Falls grades A (100/100, #1 of 17); Rapid City grades A (95/100, #15 of 17); Aberdeen grades F (58/100, #17 of 17, 7 health-based EPA violations in 5 years); Brookings grades A (97/100, #13 of 17); Watertown grades A (100/100, #2 of 17). Each city report lists the utility's violations, lead 90th-percentile result and PFAS results.
Of the 17 graded South Dakota cities, 2 cities have a D or F grade. 15 of 17 (88%) score above the national average of 87/100 across all graded U.S. cities in our dataset.
This page ranks 17 South Dakota cities from EPA's Safe Drinking Water Information System (violations and lead results, 2026Q2), UCMR5 PFAS monitoring (2023–2026) and Six-Year Review sample data (2012–2019). Each city link opens a report with the utility's violation history, lead 90th-percentile results and PFAS table. For official Consumer Confidence Reports (CCR), contact your local water utility — federal law requires all community water systems to deliver an annual CCR to customers. The South Dakota state environmental agency and the EPA's Safe Drinking Water Information System (SDWIS) also publish official water quality data.
State water quality summary and key statistics
Top 20 cities with the cleanest water
Top-ranked cities nationwide
Cities with the most concerning water
Compare water quality across all 50 states
Side-by-side water quality comparison
Which contaminants show up in South Dakota water
Certified filters matched to your contaminants