01The verdict: is Onida water safe?
Onida's drinking water has significant quality concerns based on EPA testing data. With a grade of A- (88.7/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 658 residents using surface water (rivers, lakes, or reservoirs).
4 unresolved violations on record
EPA records show open compliance items for this system. Most are administrative, but unresolved items are worth watching.
See what was cited ↓Lead is well under the limit
90th-percentile lead is 2.0 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓A flood-prone service area
7 federal disaster declarations on record. After severe weather, watch for boil-water advisories.
See the risk factors ↓Onida's drinking water received a grade of A- (88.7 out of 100), indicating good water quality. The city's 1 water system serves approximately 658 residents using purchased surface water.
Lead levels were measured at 2.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program. The system has 66 violations on record, including 16 health-based violations. 4 remain unresolved.
Onida ranks #47 out of 137 cities in South Dakota for water quality, placing it mid-range in the state. The city draws from surface water sources, which are more susceptible to seasonal runoff and agricultural contamination, requiring extensive multi-barrier treatment including coagulation, filtration, and disinfection. As a small community water system, Onida may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
02What's in Onida's water
Every contaminant flagged in Onida, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 2.0 | 15 | ppb | Inorganic | Safe |
Cities ranked by 90th-percentile lead PF PFAS in South Dakota
Cities ranked by compounds detected Cu Copper in South Dakota
Cities ranked by 90th-percentile copper
03Onida's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 66 violations on record, including 16 health-based violations. 4 remain unresolved.
All ten of the last ten years were clean — no EPA violations recorded for Onida.
▼ Down 0 ppb since 1993. Latest reading: 2 ppb (2023) — 13% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Onida's water comes from
Onida's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Purchased Surface Water
Rivers, lakes, or reservoirs — more exposed to runoff, agriculture, and seasonal swings than groundwater.
Wholesale supplier
Multi-barrier treatment: coagulation, sedimentation, filtration, and disinfection to meet EPA standards.
1 system
1 water system, operated under local government ownership.
658 people
Residents served across Onida's service area.
Surface water systems require multi-stage treatment including coagulation, sedimentation, filtration, and disinfection to meet EPA Safe Drinking Water Act standards. These sources can be impacted by seasonal changes, stormwater runoff, upstream agriculture, and industrial discharge. The system is operated by local government ownership and serves approximately 658 people through 1 water system.
| System name | PWSID | Population | Source |
|---|---|---|---|
| ONIDA | SD4600233 | 658 | Purchased Surface Water |
05Pressure on Onida's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Industrial discharge
1 facility within 10 miles reported 0 lb released to surface water in the latest EPA Toxics Release Inventory. Proximity doesn't equal tap contamination — treatment and hydrology decide — but it's pressure on the watershed.
Flood & storm history
7 federal disaster declarations on record for Sully County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
Drought
Sully County is in D1 (moderate drought) per the U.S. Drought Monitor (week of Jul 2026). Drought can raise disinfection-byproduct levels and taste/odor issues as utilities draw from lower reservoirs.
06How Onida compares
Scores for nearby South Dakota cities on one line, with the average marked.
dashed line = South Dakota average (66/100)
Onida scores 88.7/100 — above the South Dakota average of 66/100. It outscores 8 of 10 nearby cities. Full South Dakota rankings →
58.2 / 100FRapid City, SD
38.7 / 100FAberdeen, SD
41.8 / 100AWatertown, SD
91 / 100FPine Ridge, SD
43.2 / 100DBrookings, SD
46.2 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in Onida's water — not generic advice.
A basic carbon filter still helps
Onida's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Onida alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is Onida, SD tap water safe to drink?
Onida's water quality earned a grade of A- (88.7/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #47 out of 137 cities tested in South Dakota.
What contaminants are in Onida's water?
Lead was measured at 2.0 ppb (90th percentile). 66 violations are on record.
How is Onida's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Onida?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Onida's water come from?
Onida's water is sourced from Purchased surface water. The city has 1 water system serving approximately 658 residents.
What health violations has Onida's water system had?
Onida has 16 health-based violations on record. The most recent violation was recorded in August 2004. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 4 violations remain unresolved.
How does Onida's water compare to other cities?
Onida ranks #47 out of 137 cities in South Dakota (better than 66% of state cities) and #3306 out of 15382 cities nationally (79th percentile). The grade of A- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Onida's small water system affect quality?
Onida's system serves approximately 658 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 66 violations on record.