The exact distances from wells, property lines, and sinkholes, plus how much of a listing's acreage is really left for a house and two drainfields.
In Tennessee, a septic tank and drainfield must be 50 feet from a well or water supply and 10 feet from property lines. The drainfield sits 10 feet from the house (the tank, 5 feet) and 25 feet from sinkholes, streams, and drainageways. New-system designs also generally reserve a full-size backup field. Existing-system repairs can receive different site-specific approval, so use the issued permit and sketch.
These are the distances in TN Rule 0400-48-01-.11, reprinted in TDEC's July 2024 permit-documentation policy. Your own permit sketch shows how they were applied on your lot.
| Feature | Tank, dosing tank, or ATS | Disposal field | How to use the number |
|---|---|---|---|
| Water supply | 50 ft | 50 ft | Includes the drinking-water source shown on the permit sketch |
| Dwelling | 5 ft | 10 ft | Measure to the permitted structure location |
| Property line | 10 ft | 10 ft | A survey may be needed when the boundary is uncertain |
| Easement boundary | 10 ft | 10 ft | The easement itself can remove more usable area |
| Gully, ravine, dry stream bed, natural drainageway, sinkhole, stream, or cut bank | 15 ft | 25 ft | Can go up or down after a special investigation by an approved soil consultant |
| Water line | 10 ft | 10 ft | Show known and proposed lines on the site plan |
| House-to-tank connection | Not listed | 10 ft | This row protects the disposal field from the building sewer |
| Septic or dosing tank | Not listed | 5 ft | Separation shown between a tank and disposal field |
The rule has one built-in exception. The distances for gullies, ravines, dry stream beds, drainageways, sinkholes, streams, and cut banks can go up or down when soil conditions warrant it, after a special investigation by an approved soil consultant. Local conditions can require greater separation. Existing-system repairs may also need a specific TDEC decision where the usual standards cannot be met.
Start with a reliable survey; a fence or tax-map boundary may not match the surveyed line. Mark access, utility, drainage, and shared-drive easements because boundaries and restricted corridors remove possible system space.
Show the house, porches, garage, driveway, water supply, water lines, pools, barns, utilities, and other construction. A future feature can be as important as one already on the ground.
The soil consultant identifies usable soil and site limits. Steep areas, shallow rock, wet positions, fill, disturbed soil, drainageways, and sinkhole terrain can remove acreage that looks open on an aerial image.
TDEC applies the design flow, soil interpretation, system type, setbacks, tanks, piping, and field configuration. The required shape is not simply a rectangle copied from a neighboring permit.
New-system designs generally reserve a 100 percent duplication area, a full second field for the day the first one wears out. Keep that envelope reproducible in the field and free from grading, structures, and traffic.
Tennessee's septic rules don't set one statewide acreage. The lot has to be big enough to fit the house, the setbacks, the drainfield, and the backup area on usable soil. Maury County adds its own floor through zoning. For unincorporated land, the zoning ordinance effective January 1, 2026 sets these minimums:
| Maury County zone | Minimum lot area | What it means for septic |
|---|---|---|
| RG: Residential General | 1 acre | Still needs enough mapped soil for both fields |
| RR: Residential Rural | 5 acres | Acreage alone doesn't prove the soil works |
| AP: Agricultural Preservation | 15 acres | Confirm usable soil, setbacks, and the proposed use even on a large tract |
Two more lines in that ordinance matter. Lots without sewer have to meet the zoning minimum or whatever TDEC requires, whichever is larger. And the septic system has to sit on the same lot it serves, not on a neighbor's lot or in an easement. Columbia, Spring Hill, and Mount Pleasant have their own zoning, and older lots may fall under legacy districts, so check your parcel's zone first.
No, and it's the most common land-buying myth around. The five-acre number is real, but it only controls subdivision review. Rule 0400-48-01-.02 leaves divisions where every tract is five acres or more out of the definition of a subdivision, and TDEC's service guidance repeats that. It says nothing about whether the soil works.
Five acres can be mostly shallow rock, a wet bottom, steep hillside, or sinkhole drainage. Meanwhile, a one-acre lot with good soil in the right spot can permit easily. What counts is how much usable soil is left once the house, well, setbacks, drainfield, and backup field are all drawn in.
A proposed house on a five-acre tract still needs an acceptable soil evaluation and TDEC construction permit, plus whatever county planning, road-access, and deed rules apply.
The Tennessee Geological Survey's Maury County atlas maps sinkholes, unstable ground, flood-prone areas, and rock units across the county. Out in the field, a sinkhole here is often a wide, shallow bowl in a pasture rather than an open hole, and the water draining into it matters as much as the low point.
So the 25-foot field distance starts at the edge of the whole depression, and the consultant has to map where that edge is. The county atlas tells you sinkholes are likely in an area. Only a site visit tells you where the line falls on your lot.
Pull your permit and site sketch first. TDEC has a modification service for exactly this: adding bedrooms, or building a pool, garage, shop, or barn that touches the drainfield or backup area. Our records guide shows how to find the TDEC septic permit and site sketch.
Sketch the new project on that drawing and ask TDEC which review applies. Do it before you pay a design deposit or start grading. Shifting a pool 20 feet on paper is free; moving it after it's poured isn't.
About our sources. Maury Septic uses the sources listed below, including TDEC's current permit-sketch standards, SSDS rules, online service definitions, and the Maury County geology atlas. Follow the links for the underlying rules, fees, and guidance.
Tennessee Department of Environment and Conservation
Current state policy for digital permit sketches, attachments, reproducible field references, setbacks, and FileNet record quality.
Tennessee Department of Environment and Conservation
Official rule index for permits, design, maintenance, soil consultants, installers, and fees.
Tennessee Department of Environment and Conservation
Conventional, repair, and alternative-system applications, plus soil-map requirements.
Tennessee Department of Environment and Conservation
State mapping standards for soil depth, restrictive layers, drainage, absorption rates, slope, site features, and SSDS interpretations.
Maury County Government
Current zoning rules for unincorporated Maury County, including lot standards and the requirement that septic systems and fields remain on the lot they serve.
Tennessee Geological Survey
State-published geologic, unstable-materials, flood-prone-area, mineral-resource, and sinkhole maps for Maury County.
Fifty feet. Both the tank and the drainfield have to be at least 50 feet from a water supply under TN Rule 0400-48-01-.11. If you're drilling a new well on a lot that already has septic, pull the permit sketch first and measure from where the field actually is.
Ten feet, for both the tank and the drainfield. The same 10 feet applies to easement boundaries, so a utility or shared-drive easement eats into usable space too. On a narrow lot, that 10-foot strip on each side adds up fast once the backup field is drawn in.
No. Tracts of five acres or more fall outside TDEC's definition of a subdivision, so they skip the subdivision review. Each proposed house still needs an acceptable soil evaluation and construction permit. Five acres of shallow rock fails just like half an acre of it.
It's a full-size backup drainfield spot, 100 percent of the original, that TDEC draws on your permit sketch and marks "do not disturb." If the first field ever fails, that's where the new one goes. Keep buildings, pools, driveways, and grading off it.
Twenty-five feet from the drainfield and 15 feet from the tank. The rule lets TDEC raise or lower those numbers after a special soil investigation. In Maury's limestone country a sinkhole is often a wide, shallow bowl, so the consultant measures from the edge of the whole depression.
In unincorporated Maury County, the 2026 zoning ordinance sets minimums of 1 acre in Residential General, 5 acres in Residential Rural, and 15 acres in Agricultural Preservation. Lots without sewer must also be as large as TDEC requires, whichever is bigger. Cities like Columbia and Spring Hill have their own zoning.
This form is for installation, replacement, repair, and aerobic service requests. It does not calculate legal boundaries, map soil, set setbacks, or issue a TDEC permit.
Related: Tennessee septic rules explained · septic permit guide · soil and site evaluation · sinkholes and septic · building over the drainfield · failed soil test options · septic records lookup · septic system cost · subdividing land with septic · wells and septic
Keep your permit, system sketch, and service records together. They help the next professional understand your property.