Off-Grid Living in Mercer County, Ohio

I'll be upfront: Mercer County, Ohio is one of those places where the honest answer to "can I go off-grid here?" is "it depends which township you're standing in." There's no single countywide zoning code covering every acre. Zoning here is a patchwork of township and village authority, with about 63% of the county's 48 municipalities having adopted zoning, according to the Mercer County Regional Planning Commission (MCRPC). Some township land, like the western part of Jefferson Township, has no zoning at all, and state-owned land isn't subject to local zoning either.

The county does maintain its own zoning code (effective 2001), administered jointly with township and village zoning inspectors, but whether it applies to your specific parcel depends entirely on that township or village. My advice: before you buy or plan anything, call the zoning inspector for the specific township or village where the land sits. Mercer County publishes a pamphlet listing inspectors and phone numbers for each township, which is the fastest way to get a real answer.

On dwellings, I couldn't find county-specific rules on tiny homes or RV occupancy. The zoning permit process does route larger projects, manufactured homes, and 3+ unit residential buildings to a state-certified building department, historically the Miami County Building Regulations office. For a single tiny home or RV, you're likely dealing with whatever the township zoning inspector says, so ask directly.

Septic is where the county gets specific. The Mercer County Health District runs its own Household Sewage Treatment System (HSTS) program under state OSTS rules, with local rules that took effect in 2021. You'll need a soil evaluation and a permit before building, replacing a system, or splitting a parcel. Zoning permits actually require a sanitary sewer permit number before they'll issue, which ties your building approval directly to your septic approval.

Wells are regulated the same way, by the Health District under Ohio Revised Code and Administrative Code, with pre-drilling site inspections for setbacks. Rainwater harvesting is allowed, but new-construction cisterns fall under state code requirements the Health District administers locally.

Greywater and full utility disconnection are the fuzziest areas. I found no Mercer County-specific greywater policy, so it presumably falls under the state Ohio Department of Health framework administered by the local Health District. Living fully off-grid (no utility hookups) isn't addressed as its own category either, but since a certificate of occupancy seems to hinge on an approved septic system, you'll need at minimum a compliant wastewater solution even if you skip electric and municipal water.

Bottom line: this county rewards homework. Call the township, call the Health District, confirm before you build.