Who serves this area
Homes in the Town of Mount Pleasant are served by Mount Pleasant Waterworks (MPW). Depending on where you live, your tap may receive reverse-osmosis-treated groundwater, treated surface water purchased from Charleston Water System, or a blend of the two. Check your bill, or ask MPW at (843) 884-9626, if you want to know which source serves your street.
The official current report is the 2025 Annual Drinking Water Quality Report, covering January 1–December 31, 2025, linked from mountpleasantwaterworks.com/AnnualWaterReport.
Where the water comes from and how it is treated
MPW's groundwater comes from the Charleston Aquifer, from wells about 2,000 feet deep. That water is treated at MPW's reverse-osmosis plants, then disinfected with chloramine. About 10% of the groundwater is blended back after RO treatment to restore minerals and naturally occurring fluoride. MPW does not add chemical fluoride.
MPW also buys treated surface water from Charleston Water System (Bushy Park Reservoir and the Edisto River, treated at the Hanahan plant).
Sources: MPW 2025 Annual Drinking Water Quality Report (PDF); MPW water quality reports.
How to read these numbers
Utilities must meet a legal limit — usually a Maximum Contaminant Level (MCL), a Maximum Residual Disinfectant Level (MRDL) for disinfectants, or an Action Level (AL) for lead and copper. The health goal, or Maximum Contaminant Level Goal (MCLG), is the level below which EPA expects no known health risk. It is often lower than the legal limit, and it is not a violation if a result is above the health goal but below the legal limit.
PFAS figures below are compared with EPA's current legal limits of 4 parts per trillion (ppt) for PFOA and PFOS, and 10 ppt for PFHxS, PFNA, and HFPO-DA (GenX). Those limits were finalized in 2024. They are not yet being enforced as violations. The original compliance deadline is 2029; EPA has since discussed extending it to 2031. Until a later deadline is finalized, treat 2029 as the date utilities have been told to plan for.
Sources: EPA PFAS drinking water rule; EPA announcement on PFOA and PFOS MCLs; Charleston Water System 2026 Water Quality Report, p. 14.
What's in Mount Pleasant water
MPW reports that drinking water met or was better than all regulatory standards in 2025. Because the town has two supplies, the tables are split. Lead and copper are measured at customer taps and apply system-wide.
Reverse-osmosis treated groundwater
| Substance | Level | Legal limit | Health goal (MCLG) | Year | Notes |
|---|---|---|---|---|---|
| Chloramine | 3 ppm | 4 ppm MRDL | 4 ppm MRDLG | 2025 | Water additive used to control microbes. |
| Haloacetic acids (HAA5) | 10 ppb (range ND–18.6) | 60 ppb | None set | 2025 | Disinfection byproduct. |
| Total trihalomethanes (TTHM) | 8 ppb (range ND–15.8) | 80 ppb | None set | 2025 | Disinfection byproduct. |
| Fluoride | 0.6 ppm (range 0.27–0.6) | 4 ppm | 4 ppm | 2025 | Naturally present in the aquifer; MPW does not add fluoride. |
| Nitrite (as nitrogen) | 0.067 ppm | 1 ppm | 1 ppm | 2021 | Most recent result in this report. |
| Sodium | 73 ppm (range 51–73) | No MCL | — | 2021 | No health-based legal limit. |
| E. coli (distribution system) | 0 positive samples | Routine/repeat sampling rules | 0 | 2025 | |
| Alpha emitters | 0.428 pCi/L | 15 pCi/L | 0 pCi/L | 2022 | |
| PFBS (UCMR 5) | 2.93 ppt (range ND–4.4) | No standalone MCL | — | 2024–2025 | |
| PFBA (UCMR 5) | 2.90 ppt (range ND–6.3) | No MCL | — | 2024–2025 | |
| PFHxA (UCMR 5) | 3.55 ppt (range ND–5.1) | No MCL | — | 2024–2025 | |
| PFOS (UCMR 5) | 6.63 ppt (range 5.6–8.4) | 4 ppt (future standard; not a current violation) | 0 ppt | 2024–2025 | |
| PFOA (UCMR 5) | 3.65 ppt (range ND–5.5) | 4 ppt (future standard; not a current violation) | 0 ppt | 2024–2025 | The average is below 4 ppt; the high end of the range is above it. |
| PFPeA (UCMR 5) | 5.18 ppt (range 4.4–6.0) | No MCL | — | 2024–2025 |
Nitrate was not listed in the 2025 RO groundwater table in the official report, so it is not shown here.
Wholesale surface water (from Charleston Water System)
| Substance | Level | Legal limit | Health goal (MCLG) | Year | Notes |
|---|---|---|---|---|---|
| Chloramine | 3.0 ppm | 4 ppm MRDL | 4 ppm MRDLG | 2025 | |
| Total organic carbon | 61% removal (range 47–61%) | Treatment technique | — | 2025 | |
| Fluoride | 0.24 ppm (range 0.07–0.24) | 4 ppm | 4 ppm | 2025 | |
| Nitrate (as nitrogen) | 0.14 ppm | 10 ppm | 10 ppm | 2025 | |
| Sodium | 9.4 ppm | No MCL | — | 2025 | |
| Turbidity | Highest 0.09 NTU (range 0.07–0.09); 100% of samples below 0.3 NTU | Treatment technique (0.3 NTU) | — | 2025 | |
| PFBS (UCMR 5) | 3.9 ppt (range 3.7–4.3) | No standalone MCL | — | 2023–2025 | |
| PFBA (UCMR 5) | Not detected | No MCL | — | 2023–2025 | |
| PFHxA (UCMR 5) | 4.2 ppt (range 3.8–4.6) | No MCL | — | 2023–2025 | |
| PFOS (UCMR 5) | 5.8 ppt (range 5.2–6.5) | 4 ppt (future standard; not a current violation) | 0 ppt | 2023–2025 | |
| PFOA (UCMR 5) | 4.3 ppt (range 4.1–4.7) | 4 ppt (future standard; not a current violation) | 0 ppt | 2023–2025 | |
| PFPeA (UCMR 5) | 4.6 ppt (range 4.4–5.0) | No MCL | — | 2023–2025 |
Source for both tables: MPW 2025 Annual Drinking Water Quality Report, water-quality tables (report pages 4–5).
Lead
MPW states that, based on maintenance records, inspections, and EPA-approved modeling, there are no lead service lines in its water distribution system. You can look up an address on MPW's service line inventory map.
Lead can still come from plumbing inside a home, especially one built before the 1986 federal lead ban. In 2023 tap sampling, the 90th percentile was 1.1 ppb for lead (action level 15 ppb; health goal 0) and 0.061 ppm for copper (action level 1.3 ppm). No samples exceeded either action level.
If you are concerned, MPW will schedule testing: (843) 884-9626 or jdeepe@mpwonline.com.
Source: MPW 2025 Annual Drinking Water Quality Report, lead section and lead-and-copper table.
PFAS
MPW published UCMR 5 results for both of its supplies. In RO-treated groundwater, average PFOS was 6.63 ppt (range 5.6–8.4) and average PFOA was 3.65 ppt (range ND–5.5). In purchased Charleston Water surface water, average PFOS was 5.8 ppt (range 5.2–6.5) and average PFOA was 4.3 ppt (range 4.1–4.7). Several of those averages and ranges are at or above EPA's future 4 ppt standard. That is not a current violation. MPW notes that its RO process is designed to remove a broad range of contaminants; the results above are what the 2025 report actually measured.
Source: MPW 2025 Annual Drinking Water Quality Report, UCMR 5 tables; also described in MPW's July 2026 report announcement.
Disinfection byproducts
On the RO-groundwater supply, 2025 TTHM was 8 ppb (legal limit 80) and HAA5 was 10 ppb (legal limit 60). Those are low compared with the limits. The surface-water table in the 2025 report lists chloramine and TOC removal for that supply, but it does not repeat a separate TTHM/HAA5 line for wholesale water.
Source: MPW 2025 Annual Drinking Water Quality Report, RO groundwater table.
What the utility report can't tell you
A utility report describes water as it leaves the treatment plant and as it moves through the public system. It cannot tell you what comes out of your own faucet.
- Your pipes and fixtures. Lead and copper usually come from a home's service line, solder, or fixtures — especially in homes built before the 1986 federal lead ban — not from the water leaving the plant.
- Private wells. If you are on a well, this report does not apply to you. South Carolina does not regulate private household wells; owners are responsible for testing.
- Older homes. Even when a utility meets every legal limit, a single older home can still have higher lead or copper at the tap.
A useful next step
If you want a snapshot of your own tap water, Auraven Labs offers a free in-home water check. During the visit we measure pH, conductivity, TDS (total dissolved solids), and salinity. Those readings do not detect lead, bacteria, PFAS, or other contaminants, and they do not determine whether your water is safe.
If you want a certified laboratory analysis of your tap water, the City Basic lab test is available for $329.