Charleston – South Carolina
Charleston Water System (CWS) serves approximately 450,000 residents across the Charleston metropolitan area, including portions of Berkeley, Dorchester, and Charleston counties. The utility manages over 1,800 miles of water mains, one major drinking water treatment plant, and multiple pumping stations, delivering an average of 55 million gallons daily to this historic coastal city.
Charleston draws its drinking water primarily from the Edisto River and the Bushy Park Reservoir, with the latter serving as the main source for the Hanahan Water Treatment Plant. As a coastal city at sea level, Charleston faces unique water challenges including saltwater intrusion, tidal influences, and increasing flood events. The city has invested significantly in water system resilience, implementing over $250 million in infrastructure improvements over the past decade. Charleston’s water management approach balances historical preservation considerations with infrastructure modernization, water quality protection, and comprehensive climate adaptation planning for this vulnerable coastal community.
Charleston Water Quality: Current Status (2024-2025)
Latest Testing Results
- Lead Levels: The most recent testing period (January-December 2023) showed 90th percentile lead levels of 4.2 parts per billion (ppb), well below the EPA action level of 15 ppb, reflecting effective corrosion control and targeted infrastructure replacement efforts.
- Testing Scope: Charleston Water System conducts over 100,000 water quality tests annually, including enhanced monitoring in historical districts with older infrastructure and comprehensive source water surveillance.
- Compliance Status: Charleston’s water meets all federal and state drinking water standards, maintaining consistent compliance with EPA and South Carolina Department of Health and Environmental Control regulations.
Diverse Water Supply
- Bushy Park Reservoir: Primary source (approximately 80% of supply) located in Berkeley County, providing a consistent, protected water source despite seasonal variations in water quality.
- Edisto River: Secondary source (approximately 20% of supply) that provides additional capacity during peak demand periods and drought conditions.
- Watershed Protection: Comprehensive source water protection programs including land conservation efforts, buffer zone preservation, and watershed monitoring in collaboration with neighboring jurisdictions and conservation groups.
Treatment Excellence
- Advanced Filtration: The Hanahan Water Treatment Plant employs multi-stage treatment processes including conventional sedimentation, granular activated carbon filtration, and enhanced disinfection systems.
- Disinfection System: Utilizes chloramine as a secondary disinfectant, providing longer-lasting protection while reducing disinfection byproduct formation compared to free chlorine.
- Corrosion Control: Optimized pH adjustment and orthophosphate addition prevents leaching of lead and copper from pipes, with treatment parameters continuously monitored and adjusted based on extensive water chemistry data.
Infrastructure Adaptation
- Capital Improvement Program: Over $250 million invested in water system upgrades since 2010, addressing aging infrastructure, saltwater intrusion prevention, and system resilience in the face of increasing flood events.
- Historic District Considerations: Specialized pipe replacement programs that balance preservation of historic streetscapes with critical infrastructure needs, using trenchless technology where appropriate.
- Smart Water Technology: Deployment of advanced metering infrastructure, pressure monitoring systems, and real-time water quality sensors to optimize system performance and rapidly identify potential issues.
Climate Resilience Planning
Charleston has developed a forward-thinking climate adaptation strategy specifically addressing the unique challenges facing a low-elevation coastal city. The “Charleston City Plan” and “Sea Level Rise Strategy” include water system hardening measures, flood-resistant infrastructure design, and emergency response protocols for major storm events. CWS has elevated critical water infrastructure components above projected flood levels and implemented backup power systems at key facilities. The utility is also investigating alternative water sources and advanced treatment technologies to address increasing saltwater intrusion concerns as sea levels rise. Charleston’s comprehensive planning approach recognizes the interconnected nature of stormwater management, drinking water protection, and wastewater services in a changing coastal environment.
Recommendations for Charleston Residents
Schedule Water Testing
Request free water quality testing through Charleston Water System by calling (843) 727-6800. Testing is particularly important for homes in the historic districts or buildings constructed before 1986 that may have older plumbing materials.
Consider Water Filters
For homes in the historic peninsula area or buildings constructed before 1986, consider using NSF-certified filters (Standard 53) for drinking and cooking water. Filters can also help reduce potential taste and odor concerns during seasonal algal blooms in source waters.
Implement Flood Protection
Given Charleston’s vulnerability to flooding, protect your home’s water systems by installing backflow prevention devices on plumbing fixtures and considering flood-resistant materials for basement or first-floor plumbing. Charleston Water System offers a rebate program for qualifying backflow prevention installations.
Flush After Prolonged Absences
If your home has been vacant for more than a week, run cold water taps for 3-5 minutes before using water for drinking or cooking. This is particularly important in Charleston’s historic homes with older plumbing systems, as water that sits in pipes can absorb trace metals over time.
Report Flooding Issues
Report water main breaks, unusual water quality, or flood-related concerns immediately to Charleston Water System at (843) 727-6800. During king tides or storm events, prompt reporting helps the utility prioritize emergency response and protect water quality.
Frequently Asked Questions
Is Charleston’s tap water safe to drink?
Yes, Charleston’s tap water is safe and consistently meets all federal and state drinking water standards. The Hanahan Water Treatment Plant employs multiple treatment barriers including coagulation, sedimentation, filtration through granular activated carbon, and disinfection with chloramines.
Charleston Water System conducts over 100,000 water quality tests annually, monitoring for more than 200 regulated and unregulated contaminants. Lead testing results are well below EPA action limits, though residents in historic homes or buildings constructed before 1986 may want to use certified filters as an additional precaution.
During certain times of year, especially summer months, you may notice occasional taste and odor changes due to naturally occurring algae in our source waters. While aesthetically noticeable, these compounds are effectively removed through our treatment process and pose no health concern. If you have specific concerns about your water quality, Charleston Water System offers free testing to customers.
How does flooding affect Charleston’s water quality?
Charleston’s unique coastal location makes flooding a frequent concern, but several protective measures ensure water quality remains consistent:
• Protected Source Water: Our primary water source, Bushy Park Reservoir, is located inland and less vulnerable to coastal flooding and saltwater intrusion
• Elevated Infrastructure: Critical water treatment and pumping facilities have been elevated above projected flood levels and equipped with backup power systems
• Monitoring Systems: Enhanced water quality monitoring during and after flood events ensures early detection of any potential issues
• Distribution System Protection: Pressure maintenance throughout the system prevents contamination from entering water mains even during flood conditions
During major flood events, Charleston Water System implements additional water quality testing and may temporarily increase disinfectant levels as a precautionary measure. Customers rarely experience water quality impacts, even during significant flooding.
What improvements has Charleston made to its water system?
Over the past decade, Charleston Water System has invested over $250 million in water system improvements:
• Treatment Plant Optimization: Enhanced the Hanahan Water Treatment Plant with state-of-the-art filtration technology and monitoring systems
• Historic District Infrastructure: Specialized replacement programs for water mains in the historic peninsula, using minimally invasive techniques
• Flood Resilience: Elevated pumping stations, installed flood barriers, and implemented backup power systems at critical facilities
• Smart Water Network: Deployed advanced metering infrastructure and pressure monitoring systems to detect leaks and optimize operations
• Source Water Protection: Partnered with conservation organizations to protect and enhance watershed areas surrounding water sources
These investments have significantly improved system reliability, particularly during extreme weather events, and ensure Charleston’s ability to provide high-quality water despite increasing climate challenges.
How is Charleston addressing saltwater intrusion concerns?
As a coastal community with rising sea levels, Charleston has implemented a multi-faceted approach to address saltwater intrusion:
• Source Water Diversification: Maintaining multiple water sources with primary reliance on the inland Bushy Park Reservoir
• Advanced Monitoring: Conductivity sensors throughout the distribution system provide early detection of potential saltwater infiltration
• Treatment Process Adaptations: Enhanced treatment capabilities that can address varying levels of salinity in source waters
• Infrastructure Hardening: Strategic valve placement and distribution system modifications to isolate vulnerable coastal areas if necessary
• Research Partnerships: Collaboration with regional universities and agencies to model future saltwater intrusion scenarios and develop mitigation strategies
To date, Charleston’s drinking water sources have not experienced significant saltwater intrusion impacts, but the utility continues to develop long-term strategies to address this potential challenge as sea levels rise.
Contaminants of Concern
PFAS Compounds
Source: Industrial processes, firefighting foams, and consumer products that may contaminate source waters, particularly in areas with historical industrial activity
Health Effects: Potential links to increased cholesterol levels, changes in liver enzymes, small decreases in infant birth weights, and increased risk of certain cancers with long-term exposure to high levels
Current Status: Charleston Water System voluntarily monitors for PFAS compounds with levels consistently below EPA’s proposed regulatory limits; the utility has established activated carbon treatment processes that provide effective PFAS reduction
Lead
Source: Lead service lines and plumbing materials in homes built before 1986, particularly in Charleston’s historic districts; Charleston Water System has undertaken extensive inventories to identify remaining lead service connections
Health Effects: Developmental delays in children, reduced IQ, learning difficulties, kidney problems, and cardiovascular effects in adults
Current Levels: 90th percentile value of 4.2 ppb, well below EPA action level of 15 ppb EPA Limit: Action level 15 ppb, but no level of lead is considered safe
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