Water Quality Reports

Understanding Water Quality Reports:

MRL -- Minimum Reporting Level
Smallest amount that can be measured by the test instrument. Any "Result" below the MRL is considered Non-Detect, or not present.

MCL -- Minimum Concentration Level
Regulatory limit defining the safe/acceptable amount of a substance.

Result Column:
Amounts shown as <X equal Non-Detect, or not present. Example: <2.0
Bold numbers illustrate a substance found in concentrations above the MRL (substances actually detected.)

mg/L             milligrams per liter, which equals parts per million (ppm)
ng/L              nanograms per liter, which equals parts per trillion (ppt)
umhos/cm   micromhos per centimeter

Monthly Water Quality Report

Provides averages for water quality parameters.
2019: January - March data   *Report has a lag time of one month.

Ad-Hoc Water Quality Reports

We tested our water in response to community concerns about these substances:
    (7/12/17) - Pesticides & herbicides (Report 1)    None found.
    (7/12/17) - Pesticides & herbicides (Report 2)    None found.
(8/02/17) - GenX & PFCs    No GenX found.  PFCs present far below EPA Health Advisory.

Annual Water Quality Report

/ Consumer Confidence Report (CCR)
This report tells you where our water comes from and how it’s treated. It also provides a summary of our water quality test results and tells you whether we met all regulatory requirements. Water utilities are required to produce this report each year by July 1. Our report is typically available in May for the prior year's data.

Archived reports

Questions/Request hard copies

(843) 727-6800 or email

Drinking Water Fluoridation (

Position Statement


Adopted by the Board of Commissioners October 24, 2017

The Charleston Water System (CWS) supports the recommendations of the World Health Organization, American Medical Association, Canadian Medical Association, Centers for Disease Control and Prevention (CDC), American Dental Association, Canadian Dental Association, South Carolina Dental Association and other professional organizations in the medical community, for the proper fluoridation of public water supplies as a public health benefit. We also support regular scrutiny of the most current peer reviewed research on fluoride and the positions of the medical and dental community.

We adjust the naturally occurring level of fluoride in our drinking water in a responsible, effective, and reliable manner that includes monitoring and controlling fluoride levels as mandated by state and/or federal laws, regulations and recommendations. We carefully monitor and adjust potable water to achieve the scientifically recommended concentration of fluoride for protection against dental caries, which is 0.7 parts per million. Our annual cost for this program is about $110,000, which equates to $0.25 per person across the approximately 450,000 people in our water service area.

The CWS participates in the fluoridation of water under the guidance of the South Carolina Department of Health and Environmental Control (SCDHEC), Oral Health Division. SCDHEC coordinates their program in conjunction with the CDC and the U.S. Department of Health and Human Services.

If there are questions regarding these programs, please contact:
Division of Oral Health
2100 Bull Street, Columbia, S.C. 29201
P: (803) 898-9577
F: (803) 898-2065

Unregulated Compounds in Drinking Water (Position Statement)

Adopted by the Board of Commissioners; July, 24, 2018

Charleston Water System (CWS) is committed to meeting or exceeding all drinking water regulations put forth by the South Carolina Department of Health and Environmental Control (SCDHEC), which coordinates their program with oversight from the United States Environmental Protection Agency (EPA.) As a regulated water utility, CWS employs licensed water treatment professionals and solely relies on SCDHEC and the EPA to evaluate health risks and establish drinking water guidelines and regulations.

Supporting public health is a key component of CWS’s mission. Consequently, in an effort to inform, empower, and protect our customers, and to provide them with high quality drinking water, CWS voluntarily exceeds established regulatory requirements by testing for compounds known or anticipated to occur in public water supplies and those with non-regulatory EPA Health Advisory limits.

CWS takes the following position on unregulated compounds, categorizing them into three groups, each with a distinct plan of action:

I. Compounds under the EPA’s Unregulated Contaminants Monitoring Rule (UCMR)

By desire and law, CWS participates in each iteration of the EPA’s UCMR. This rule dictates that CWS collects data for up to 30 specific compounds which are not regulated by the National Primary Drinking Water Regulations, but are known or anticipated to occur in public water systems, and therefore may warrant future regulation under the Safe Drinking Water Act (SDWA). The UCMR provides EPA, state regulators, and water utilities with scientifically-valid data on the occurrence of these compounds in drinking water in the United States, which then permits assessment of the potential population being exposed and the predicted levels of exposure. This data is one of the primary sources of information the EPA uses to prioritize and develop future regulatory decisions for unregulated compounds. All CWS results from the UCMR monitoring are reported on the CWS website and detectable concentrations are reported in the CWS annual Consumer Confidence Report (CCR)/Water Quality Report.

Voluntary testing:
If a compound is detected in CWS treated drinking water during any UCMR testing event, CWS will voluntarily establish a testing schedule for that compound that is more frequent than required by the UCMR.
Unregulated Contaminants Under UCMR
If the EPA develops regulatory limits for any compound found during the UCMR program, CWS will adhere to any new regulations. If additional treatment is required, CWS will upgrade the treatment process to ensure compliance, within established regulatory limits.

II. Unregulated Compounds with EPA Health Advisories
The EPA Office of Water publishes Health Advisories (HAs) as informed guidance for unregulated compounds. They are not legally-enforceable federal standards. However, CWS voluntarily monitors its treated drinking water for all compounds identified in the EPA’s 2018 Edition of the Drinking Water Standards and Health Advisories Tables (DWSHA), and this process occurs in five-year cycles.

Voluntary testing:
The first year includes quarterly monitoring of treated drinking water exiting the CWS Hanahan Water Treatment Plant. Sampling will occur mid-month of each quarter (August, November, February, May) to examine seasonal variations. Subsequent years will consist of annual monitoring of any compounds detected in the inaugural sampling. To further examine seasonal variation, annual sampling will rotate through each quarter, as described above.

Unregulated Compounds with EPA Health Advisories
If a compound is present in concentrations below the EPA Health Advisory level, CWS may or may not employ additional sampling or treatment actions. However, if a compound with an EPA Health Advisory is present in CWS treated water in concentrations higher than its EPA Health Advisory level, CWS will evaluate current treatment options and develop a plan of action to meet the Health Advisory, if reasonably possible. After the five-year cycle concludes, this voluntary monitoring program will be re-evaluated utilizing the most recent version of the DWSHA.

III. All Other Unregulated Compounds
CWS does not routinely test for these compounds and does not plan to alter its water treatment process if any are present because the EPA and SCDHEC have not deemed any of these compounds a threat to human health at quantities that may exist in drinking water.

Ultimately, it’s impossible to test for all known compounds because they number in the billions, and new compounds are being developed every day.

Test Results
CWS test results for unregulated compounds, if detected, are posted to www.charlestonwater.com. They’re also included in the CWS annual Consumer Confidence Report/Water Quality Report available online and in print, and provided annually to SCDHEC as required.

Evaluating The Results
Almost every compound, including pure water, has a hazard profile. Health risk is an indication of the probability that harm could occur under defined conditions of concentration and exposure.

When evaluating the compounds found in any drinking water supply, it’s important to consider that science and technology continue to advance, enabling detection of more compounds at continually lower levels in drinking water.

The question becomes, which compounds, and at what concentrations, and in what quantities consumed, over what time period, can potentially cause harm from exposure via drinking water.

As with all CWS policies, the CWS Commissioners and executive Officers are responsible for ensuring the compliance of this position statement. And as such may opt to modify such position as it deems in its best interest and in the interest of its valued customers, as necessary.