The water provided by the Charleston Water System consistently meets or surpasses all mandated federal and state safety requirements established under the Safe Drinking Water Act. This means that, from a regulatory standpoint, the water is considered safe for general consumption. However, the presence of certain contaminants, while legally compliant, and the potential for issues within home plumbing systems warrant a detailed look at the water’s journey from its source to the consumer’s tap.
The Water Source and Treatment Process
The region’s drinking water originates from two primary surface water sources: the Bushy Park Reservoir (the main supply) and the Edisto River. Both sources feed raw water through deep tunnels to the Hanahan Water Treatment Plant, the largest facility of its kind in South Carolina. Because the source water is surface-based, it requires a complex and multi-stage cleaning process to ensure potability.
Once the raw water arrives at the plant, treatment begins with the addition of aluminum sulfate (alum), which acts as a coagulant. This chemical causes microscopic impurities and particles to clump together into heavier masses called floc, a process known as flocculation. The water is then moved into large sedimentation basins where the heavy floc particles sink to the bottom and are removed from the main water stream.
Following the initial cleansing, the water passes through large filters composed of layers of sand, gravel, and anthracite coal, which remove any remaining microscopic contaminants and microorganisms. The final step is disinfection, achieved using chlorine dioxide and chloramines, a stable disinfectant formed by combining chlorine and ammonia. A corrosion inhibitor, orthophosphate, is also added to protect the distribution system, and the naturally occurring fluoride level is adjusted to promote dental health.
Regulatory Standards and Compliance Monitoring
The safety of the treated water is ensured by a regulatory framework overseen by the Environmental Protection Agency (EPA) and state-level agencies, such as the South Carolina Department of Health and Environmental Control. The EPA establishes Maximum Contaminant Levels (MCLs) for a wide range of substances, representing the highest amount of a contaminant allowed in public drinking water. The Safe Drinking Water Act mandates utilities to maintain levels below these established thresholds.
Compliance is demonstrated through rigorous, mandatory testing schedules that require thousands of water analyses monthly. These tests monitor for microbiological contaminants, which can cause immediate illness, and chemical contaminants, such as heavy metals and organic compounds. The utility must regularly submit its testing data to the state, and the results consistently confirm that the water leaving the Hanahan plant is fully compliant with all federal and state MCLs.
Furthermore, the utility participates in the voluntary Partnership for Safe Water, which commits the system to treating water to quality levels that exceed legal requirements.
Infrastructure Concerns and Specific Contaminants
While the water is treated to high standards at the plant, the aging infrastructure of the distribution system can introduce specific concerns before the water reaches a resident’s tap. Lead and copper can leach into the water from older service lines, plumbing fixtures, and internal home soldering. To combat this, the Charleston Water System adds orthophosphate, a food-grade corrosion inhibitor, which creates a protective layer inside the pipes to prevent the leaching of these metals.
Disinfection byproducts (DBPs) represent another concern, particularly Total Trihalomethanes (TTHMs), which form when disinfectants like chlorine react with naturally occurring organic matter in the source water. Although the utility’s TTHM levels remain below the EPA’s enforceable MCL, internal monitoring has sometimes shown concentrations that exceed more protective, non-regulatory health guidelines set by independent organizations. Bromodichloromethane, a component of TTHMs, is one of the compounds that often registers at levels significantly higher than these advisory benchmarks.
Emerging contaminants, such as per- and poly-fluoroalkyl substances (PFAS), have been detected in the system’s source water. These chemicals, often associated with industrial use and military sites, are not yet fully regulated by a federal MCL, though the EPA is moving toward establishing one. The Charleston Water System has reported detectable concentrations of PFAS compounds like PFOS and PFOA. While these levels are sometimes below current health advisories, they remain a focus of ongoing national concern and local monitoring.
Accessing Current Water Quality Reports and Alerts
By law, the Charleston Water System must publish an annual Consumer Confidence Report (CCR), which details the previous year’s testing results for all regulated contaminants. This report is typically made available to the public every May and is easily accessible on the utility’s official website. The CCR provides a snapshot of the water source, its contents, and how detected levels compare to the EPA’s established Maximum Contaminant Levels.
The utility is required to issue immediate public alerts, such as a boil water advisory, through local media and direct notifications when necessary. Residents who have concerns about their private plumbing, particularly in older homes, can request a free lead and copper testing kit from the Charleston Water System to determine the final water quality at their specific faucet.