Off-Grid Living in Williamson County, Illinois

I've been digging into Williamson County, Illinois (the Southern Illinois one near Marion, Herrin, and Carterville, not the Texas or Tennessee counties that keep popping up in searches), and here's the honest picture for anyone thinking about going off-grid here.

Zoning first. Unlike a lot of rural Illinois counties that have no zoning at all, Williamson County actually adopted a countywide Zoning Ordinance back in 2012, and it's been tweaked since. This matters a lot: it means where you buy land determines what you can do with it. The county's rural districts generally allow one dwelling per five acres, and some of those districts allow single-wide mobile homes while "rural estate" districts do not. The county has also been renaming districts (Rural Development, Rural Preservation, etc.), but from what I can tell the densities haven't really changed, just the labels. The Williamson County Planning/Zoning Department is who to call before you buy anything.

Dwellings, tiny homes, RVs. I couldn't find county text spelling out tiny-house minimum square footage or whether you can live in an RV full-time. What I can confirm is that the county's zoning districts already treat manufactured/mobile homes differently by district, so I'd assume tiny homes and RVs get sorted the same way, permitted in some zones, restricted in others. Confirm directly with Planning/Zoning.

Building permits. The county runs its own Building Permit Ordinance and application process, separate from town building departments in Herrin, Marion, or Carterville if you're inside those municipal limits. Illinois also adopted a new statewide building code baseline as of January 1, 2025, which the county's building department would enforce alongside its own ordinance.

Septic and composting toilets. This one's permitted but not a free-for-all. The Franklin-Williamson Bicounty Health Department handles septic and private sewage permitting locally, acting under authority delegated from the Illinois Department of Public Health (IDPH), which holds statewide rulemaking power under its private sewage disposal code. Composting toilets fall under this same framework. Local rules can be stricter than the state minimum, so check with Bi-County before you build anything.

Greywater and rainwater harvesting are both genuinely unclear here. I found no county or Bi-County Health page that specifically addresses either one. That doesn't mean they're banned, it means nobody's written a clear rule down that I could find, so you're looking at a case-by-case conversation with the Bi-County Health Department's Environmental Health division.

Wells. Permitted, and again Bi-County Health handles the local permitting as IDPH's agent, following the state well construction and inspection process.

Full utility disconnection. Also unclear. There's no ordinance I found that explicitly bans or blesses going fully off the electric grid or municipal water. In practice, it probably comes down to whether the county's occupancy requirements demand a code-compliant water and waste setup, which usually just means an approved well and septic, not necessarily a grid-electric mandate.

Bottom line: Williamson County is more regulated than some of its rural Illinois neighbors, so don't assume "rural Illinois" means anything goes. Call before you commit.