Is North Sioux City, SD Tap Water Safe to Drink?
Graded A, with 2 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
91/100
waterverge.com North Sioux City, SD — Water Quality Report
North Sioux City's drinking water received a grade of A (91 out of 100), indicating excellent water quality. The city's 1 water system serves approximately 3,042 residents using groundwater.
Lead levels were measured at 4.0 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 35 violations on record, including 0 health-based violations. 2 remain unresolved.
What to know about North Sioux City's water
North Sioux City ranks #35 out of 141 cities in South Dakota for water quality, placing it above average in the state.
North Sioux City relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
As a small community water system, North Sioux City may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is North Sioux City, SD water safe to drink?
North Sioux City's tap water meets most EPA standards but has areas that warrant attention. With a grade of A (91/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 1 water system serves approximately 3,042 residents using groundwater (wells).
Recent water quality updates for North Sioux City
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into North Sioux City's water quality assessment. Grade: A (91/100).
Federal disaster declaration (FEMA DR-4807). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4463). Flood event — may have impacted local water infrastructure.
Contaminants: 1,2-DIBROMO-3-CHLOROPROPANE, ETHYLENE DIBROMIDE.
Contaminants: Consumer Confidence Rule.
Contaminants: Consumer Confidence Rule.
Key contaminant findings
Based on the most recent EPA sampling data for North Sioux City's water supply.
Well within EPA limits.
Violation history
North Sioux City's water system has 35 total violations on record, including 0 health-based violations. 2 remain unresolved.
Flood & environmental risk
Union County has experienced 10 federally declared disasters since 1969. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Big Sioux River, Missouri River At Sioux City, Perry Creek Near Hinton, Perry Creek At 38Th Street At Sioux City.
Where does North Sioux City's water come from?
North Sioux City's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 3,042 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Big Sioux River (river), Missouri River At Sioux City (river), Perry Creek Near Hinton (river), Perry Creek At 38Th Street At Sioux City (river).
What North Sioux City residents can do
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Run cold water for 30 seconds before drinking, especially in the morning. Lead and copper leach from household plumbing when water sits in pipes.
North Sioux City's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Top industrial polluters within 10 miles of North Sioux City
Industrial polluters nearby
Reported releases to surface water by facilities near North Sioux City, ranked by pounds discharged annually.
Total reported releases to surface water: 193 lbs
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
VALMONT COATINGS INC DBA SIOUXLAND GALVANIZING CORP. SIOUX CITY, IA51111 | Zinc compounds | 177 | 9.2 mi |
CARGILL FEED & NUTRITION SIOUX CITY SIOUX CITY, IA51105 | Zinc compounds | 15 | 6.9 mi |
SIOUX CITY FOUNDRY CO SIOUX CITY, IA51105 | Lead | 1 | 6.4 mi |
STANDARD READY MIX CONCRETE CO SIOUX CITY PLANT SIOUX CITY, IA51105 | Lead | 0 | 6.0 mi |
SIOUXLAND CONCRETE CO SOUTH SIOUX CITY, NE68776 | Lead | 0 | 7.6 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Drought conditions
D2 — severe droughtUnion County is currently in D2 (severe drought) per the U.S. Drought Monitor (week of May 5, 2026). Drought can elevate disinfection-byproduct (TTHM/HAA5) levels and taste/odor issues as utilities draw from lower reservoirs.
Source: U.S. Drought Monitor, updated weekly by NDMC, USDA, and NOAA.
Flood & disaster history
Union County has experienced 10 federally declared disasters since 1969. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
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. | 4.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how North Sioux City compares by contaminant
Explore where North Sioux City ranks among all South Dakota cities for specific contaminants.
Water source & infrastructure
Where North Sioux City's water comes from
North Sioux City's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 3,042 people through 1 water system.
Water bodies near North Sioux City
North Sioux City is located near 4 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving North Sioux City
| System Name | PWSID | Population | Source |
|---|---|---|---|
| NORTH SIOUX CITY | SD4600226 | 3,042 | GW |
How North Sioux City compares
Full South Dakota rankings →North Sioux City's score of 91/100 is above the average of 66/100 among major South Dakota cities. It outscores 8 of 10 nearby cities.
Nearby cities
View South Dakota rankings →About North Sioux City, SD
Learn more about your water
Guides and resources related to North Sioux City's water quality findings.
Explore water quality across Union
Frequently asked questions
Is North Sioux City, SD tap water safe to drink?
North Sioux City's water quality earned a grade of A (91/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #35 out of 141 cities tested in South Dakota.
What contaminants are in North Sioux City's water?
Lead was measured at 4.0 ppb (90th percentile). 35 violations are on record.
How is North Sioux City'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 North Sioux City?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does North Sioux City's water come from?
North Sioux City's water is sourced from Groundwater. The city has 1 water system serving approximately 3,042 residents.
Is North Sioux City's groundwater at risk of contamination?
North Sioux City uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 35 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does North Sioux City's water compare to other cities?
North Sioux City ranks #35 out of 141 cities in South Dakota (better than 75% of state cities) and #1933 out of 15744 cities nationally (88th percentile). The grade of A reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does North Sioux City's small water system affect quality?
North Sioux City's system serves approximately 3,042 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 35 violations on record.