Is Castlewood, SD Tap Water Safe to Drink?
Graded A- — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
86.6/100
waterverge.com Castlewood, SD — Water Quality Report
Castlewood's drinking water received a grade of A- (86.6 out of 100), indicating good water quality. The city's 1 water system serves approximately 698 residents using purchased ground water.
Lead levels were measured at 1.0 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 69 violations on record, including 4 health-based violations. 3 remain unresolved.
What to know about Castlewood's water
Castlewood ranks #64 out of 141 cities in South Dakota for water quality, placing it mid-range in the state.
Castlewood purchases its water from a regional wholesaler, meaning quality depends on both the supplier's treatment and the local distribution system's condition.
As a small community water system, Castlewood may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Castlewood, SD water safe to drink?
Castlewood's drinking water has significant quality concerns based on EPA testing data. With a grade of A- (86.6/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 698 residents using groundwater (wells).
Recent water quality updates for Castlewood
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Castlewood's water quality assessment. Grade: A- (86.6/100).
1 health-based. Contaminants: Stage 1 Disinfectants and Disinfection Byproducts Rule.
Federal disaster declaration (FEMA DR-4463). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4440). Flood event — may have impacted local water infrastructure.
1 health-based. Contaminants: Coliform (TCR).
Contaminants: Consumer Confidence Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Castlewood's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Castlewood's water system has 69 total violations on record, including 4 health-based violations. 3 remain unresolved. 1 violation was issued in the last 5 years.
Flood & environmental risk
Hamlin 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 Below Watertown, Big Sioux River.
Where does Castlewood's water come from?
Castlewood's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 698 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 Below Watertown (river), Big Sioux River (river).
What Castlewood residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Castlewood's water.
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.
Castlewood'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
Drought conditions
D1 — moderate droughtHamlin County is currently in D1 (moderate 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
Hamlin 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.
Recommended water filters
Based on contaminants detected in Castlewood's water supply, we recommend the following filter types.
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. | 1.0 | 15 | ppb | Inorganic | Safe |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 2.00 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level trend (90th percentile)
See how Castlewood compares by contaminant
Explore where Castlewood ranks among all South Dakota cities for specific contaminants.
Water source & infrastructure
Where Castlewood's water comes from
Castlewood purchases its water supply from a regional wholesale provider rather than treating raw water directly.
Water quality depends on both the wholesaler's treatment standards and the condition of Castlewood's local distribution pipes and storage facilities.
Purchased water systems are common in suburban areas and smaller communities that lack the infrastructure for independent treatment.
The system is operated by local government ownership and serves approximately 698 people through 1 water system.
Water bodies near Castlewood
Castlewood is located near 2 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Castlewood
| System Name | PWSID | Population | Source |
|---|---|---|---|
| CASTLEWOOD | SD4600002 | 698 | GWP |
How Castlewood compares
Full South Dakota rankings →Castlewood's score of 86.6/100 is above the average of 66/100 among major South Dakota cities. It outscores 6 of 10 nearby cities.
Nearby cities
View South Dakota rankings →About Castlewood, SD
Learn more about your water
Guides and resources related to Castlewood's water quality findings.
Explore water quality across Hamlin
Frequently asked questions
Is Castlewood, SD tap water safe to drink?
Castlewood's water quality earned a grade of A- (86.6/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #64 out of 141 cities tested in South Dakota.
What contaminants are in Castlewood's water?
Lead was measured at 1.0 ppb (90th percentile). 69 violations are on record.
How is Castlewood'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 Castlewood?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Castlewood's water come from?
Castlewood's water is sourced from Purchased ground water. The city has 1 water system serving approximately 698 residents.
What health violations has Castlewood's water system had?
Castlewood has 4 health-based violations on record. The most recent violation was recorded in June 2021. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 3 violations remain unresolved.
Is Castlewood's groundwater at risk of contamination?
Castlewood 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 69 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 Castlewood's water compare to other cities?
Castlewood ranks #64 out of 141 cities in South Dakota (better than 55% of state cities) and #4619 out of 15744 cities nationally (71th percentile). The grade of A- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Castlewood's small water system affect quality?
Castlewood's system serves approximately 698 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 69 violations on record.