Sourced from the Mount Pleasant Code of Ordinances § 155.053, Charleston County Council reporting, Mount Pleasant Waterworks program documentation, the BCDCOG 208 Water Quality Plan, and R.61-56 — last checked August 2026.
Who Issues Charleston County Septic Permits
This is the part that surprises people moving to South Carolina from almost anywhere else: Charleston County does not issue septic permits, and neither does any other South Carolina county. Onsite wastewater permitting is a state function.
The agency is the South Carolina Department of Environmental Services (SCDES), created on July 1, 2024 when Act 60 of 2023 split the old DHEC into SCDES for environmental programs and SC DPH for public health. Septic sits in SCDES’s Bureau of Regional and Laboratory Services.
Where the application goes: ATTN: OSWW, SCDES, 2600 Bull Street, Columbia, SC 29201
Statewide phone: 1-855-731-2504 (Onsite Wastewater Customer Service Center)
Online: epermitting.des.sc.gov
Form: D-1740, revision 07/2026
The Fee Is the Same in Every County: $150
Because permitting is centralized, there is one fee statewide. R.61-56 § 102.2: the Department “shall charge a fee of one hundred and fifty dollars ($150.00) to evaluate the site of a proposed onsite wastewater system.” That section was amended effective May 27, 2022. Payment is by check or money order to SCDES, and there is a $150 re-application fee if the application instructions are not followed.
There is a second route worth knowing about. You may hire a Professional Soil Classifier to do the evaluation privately, and the rules cap what they may charge at “no more than three (3) times SCDES’s fee” — so up to $450 (form DES 25-0011, dated 07/2025). People use it to skip the queue, and the queue is real: SCDES reported a 700-permit backlog in April 2023, and coastal counties have run six to fourteen weeks behind.
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If Your System Fails, You May Have to Connect
Charleston County Council voted 7–1 to require owners of failing septic systems to connect to public sewer where it is available, at their own expense, with 180 days to complete the connection. The ordinance also bars utilities from requiring annexation as a condition of providing service — a real protection, since annexation was being used as leverage.
The trigger was Snowden, an unincorporated community between Long Point Road and the Wando River marsh, where roughly 300 homes sit on septic and James Island Creek has been identified as impaired for fecal bacteria traced to failing systems.
Mount Pleasant: 500 Feet, and Real Money on the Table
Mount Pleasant has the clearest and best-dated local rule in the county. Code § 155.053: “The developer shall install public sanitary sewer lines where public sanitary sewer service is available within 500 feet” of the property. Septic is permitted only where sewer is unavailable, and must be designed to criteria approved by Mount Pleasant Waterworks.
The provision has a long, documented history — originally passed June 9, 1992, amended in 1996, 1998, 1999, 2002 and most recently October 11, 2016. It still refers to “DHEC,” which tells you the text predates the 2024 agency change rather than that the rule is stale.
The assistance is the part worth acting on
Mount Pleasant Waterworks offers a $4,500 clean water credit toward septic-to-sewer conversion, and the town adds a $4,500 match — $9,000 in total, against an average conversion cost reported at around $10,000. There is also a $15 per month septic inspection service, which about 50 households use.
If you are in Mount Pleasant on a septic system and sewer is anywhere near you, that combination changes the arithmetic substantially. We should note the $4,500 figures are single-sourced — the utility’s own program page is not machine-readable — so confirm the current amounts before budgeting.
Why the Pressure Is Real Here
Charleston County is where South Carolina’s septic problem is most visible. Statewide, 16,000 new septic permits were issued between 2018 and 2023, primarily in Charleston County. Local water advocates describe “frequent flooding, high water tables, and water-logged soils” making systems “particularly prone to failure.”
And it is shaping development decisions. In December 2025 the South Carolina Supreme Court paused a proposed 200-home development on 182 acres in Awendaw — a project that would have relied on septic systems.
The Rule That Costs the Most Money: Six Inches
South Carolina requires a minimum vertical separation of six inches between the deepest point of effluent application and the zone of saturation — the level groundwater reaches — for systems under 1,500 gallons per day (R.61-56 § 200.3).
Six inches is remarkably little, and the comparison is the fastest way to understand it:
- South Carolina — 6 inches
- North Carolina — 18 inches on the coast, 12 inches inland
- Georgia — 24 inches
- Alabama — 24 inches
South Carolina permits systems on ground its neighbors would refuse. That is legal, and it is also why Charleston is where that standard is most obviously strained. The harbor has risen 10 inches since 1950, and roughly an inch every two years since 2010. Parts of James Island now sit 1.5 inches lower than in 2007. A six-inch margin does not survive much of that.
The Repair Area Nobody Tells You About
Under R.61-56 § 200.7, a new system must reserve “a usable repair or replacement area equivalent to at least fifty (50) percent of the size of the original system” — 100 percent for community systems.
Read that as a land requirement, because that is what it is. Your lot has to hold the tank, the drainfield, and half a drainfield again in reserve, while still meeting every setback. On a tight lot that reserve area is what fails, not the drainfield itself. On a small peninsula or island lot, the reserve area is usually the binding constraint — and if you cannot site one, the county connection rule below becomes the answer by default.
Setbacks and Sizing in Charleston County
These come from R.61-56 and apply identically statewide:
- 75 feet from a private well · 100 feet from a public well
- 75 feet from the mean high water line of a stream, canal or retention pond, and from a delineated critical area line (tidal waters and tidelands)
- 25 feet from a drainage ditch · 25 feet upslope of a basement
- 5 feet from a property line · 5 feet from a building
- Rock or a restrictive horizon must sit more than 12 inches below the deepest point of effluent application
There is no state minimum lot size for a septic lot. R.61-56 requires only that the lot be large enough to hold the system, the reserve area and the setbacks. We could not retrieve Chapter 8 of the Charleston County Zoning and Land Development Regulations, which is where subdivision requirements sit. Whether the county sets a minimum lot size for septic is unverified.
When Sewer Blocks a Septic Permit
R.61-56 § 300 is blunt: “Permits for new onsite wastewater systems shall not be issued where a wastewater treatment facility is accessible for connection,” and the same bar applies to repairing or replacing a failing system.
But the state sets no distance. “Accessible” is defined only negatively — “where annexation or easements to cross adjacent property are required to connect… the wastewater treatment facility shall not be considered accessible.” So if connecting would require you to be annexed, or to cross a neighbor’s land, sewer is not accessible and your septic permit stands.
Charleston County has an unusually fragmented picture — the designated management agencies include the county itself for unincorporated areas, the City of Charleston, Folly Beach, Isle of Palms, James Island PSD, Kiawah Island, Seabrook Island and Sullivan’s Island. That list comes from a 2011 regional plan and may have changed. Current projects on the June 2026 state Clean Water priority list include Hollywood collection system repairs ($1,010,128) and two James Island PSD projects ($6,895,058 and $1,403,025). James Island PSD is also extending service at Clarks Point, connecting about 185 additional properties.
What We Could Not Confirm
The year and ordinance number of the county’s failing-septic connection requirement. Covered above — verify before relying on the 180-day clock.
Chapter 8 of the county ZLDR (subdivision regulations) — the county’s own website blocks automated access, so any county minimum lot size is unverified.
Current Mount Pleasant Waterworks connection fees. A figure of $6,345 per home appears in 2019-era reporting, with total cost approaching $10,000 — but that is a news figure, not a current published schedule, and we are flagging it as such rather than presenting it as today’s price. Also: no count or percentage of Charleston County homes on septic exists at any vintage.
Where Charleston County Sits
Charleston County runs from the peninsula out across James Island, Johns Island, Mount Pleasant and Awendaw to Edisto, on ground that is low, wet and subsiding. It has the state’s highest concentration of new septic permits and its most active septic-to-sewer conversion effort at the same time — which is why the local rules here are about getting off septic rather than about how to install it.
Nearby counties we cover: Berkeley County · Dorchester County · Colleton County. All of them run through the same state permit and the same $150 fee — what differs is the local ordinance layer, which is compared on our South Carolina septic permits by county page.
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