Tennessee · Tenn. Comp. R. & Regs. 0400-48-01-.08
Septic system requirements in Tennessee
Tank sizes, drainfield rules, setbacks, permits, and real costs — pulled from Tennessee's own code rather than a national average.
- 3-bedroom tank
- 1,000 gal
- Design flow
- 150 gpd/BR
- Typical install
- $6,000–$17,000
- Permit fee
- $200–$600
- Well setback
- 100 ft
- Permitted by
- State agency
Septic tank sizes required in Tennessee
Tennessee sizes systems on a design flow of 150 gallons per day per bedroom. The tank must meet both the bedroom table below and a 2× daily-flow detention requirement — whichever produces the larger number governs.
| Bedrooms | Design flow | Code minimum | Recommended |
|---|---|---|---|
| 1 bedroom | 150 gpd | 750 gal | 750 gal |
| 2 bedrooms | 300 gpd | 750 gal | 750 gal |
| 3 bedrooms | 450 gpd | 900 gal | 1,000 gal |
| 4 bedrooms | 600 gpd | 1,000 gal | 1,250 gal |
| 5 bedrooms | 750 gpd | 1,250 gal | 1,500 gal |
| 6 bedrooms | 900 gpd | 1,500 gal | 2,000 gal |
Source: Tenn. Comp. R. & Regs. 0400-48-01-.08. The recommended column rounds the governing requirement up to a tank size manufacturers actually stock.Run your own numbers →
Drainfield size and cost by soil type
For a three-bedroom home in Tennessee at 450 gpd. This single table explains most of the variation between quotes — the area scales inversely with how fast your soil accepts water, and the drainfield is the largest line item in the job.
| Soil | Loading rate | Absorption area | With reserve | Typical total install |
|---|---|---|---|---|
| Medium sand | 0.8 gpd/ft² | 563 ft² | 1,126 ft² | $10,000 |
| Sandy loam | 0.5 gpd/ft² | 900 ft² | 1,800 ft² | $12,700 |
| Loam | 0.4 gpd/ft² | 1,125 ft² | 2,250 ft² | $14,500 |
| Silt loam | 0.3 gpd/ft² | 1,500 ft² | 3,000 ft² | $17,400 |
| Clay loam | 0.2 gpd/ft² | 2,250 ft² | 4,500 ft² | $23,400 |
Estimates use Tennessee's cost index of 0.88× the national average. Build a line-item estimate →
Permits and who issues them
TDEC's Division of Water Resources runs the subsurface sewage disposal programme statewide, except in a handful of counties with delegated local programmes.
| Permit required | Yes |
|---|---|
| Typical fee | $200 – $600 |
| Soil evaluation | Required before permit |
| Licensed installer | Required |
| Turnaround | 2–6 weeks |
| Ongoing inspection | Not mandated statewide |
| Reserve area | 100% replacement area required |
Minimum setback distances
Measured horizontally from the drainfield unless noted. Local rules are frequently stricter, and on a small lot these numbers — not the soil — often decide the layout.
| Private water well | 100 ft |
|---|---|
| Well (septic tank) | 50 ft |
| Property line | 5 ft |
| Surface water | 50 ft |
| Building foundation | 10 ft |
Regulatory contact
Tennessee Department of Environment and Conservation — Subsurface Sewage Disposal
www.tn.gov · 888-891-8332
What makes septic hard in Tennessee
Middle Tennessee is karst limestone with thin soil over rock — sinkholes and shallow bedrock are the default, not the exception.
East Tennessee ridge-and-valley terrain gives steep slopes and highly variable soil depth over short distances.
West Tennessee loess erodes badly around disturbed ground.
Things that catch people out
- Tennessee's tank minimums are among the smallest in the country — 750 gallons for two bedrooms. That is a code floor, not a recommendation; most designers specify 1,000.
- All tanks must have two compartments with the partition two-thirds to three-quarters of the way from the inlet.
Tennessee septic questions
What size septic tank do I need in Tennessee?
A three-bedroom home in Tennessee requires a minimum 900 gallon tank under Tenn. Comp. R. & Regs. 0400-48-01-.08. Design flow is 150 gallons per day per bedroom, and the tank must also hold 2 times daily flow, so the practical recommendation is 1,000 gallons.
Do I need a permit for a septic system in Tennessee?
Yes. TDEC's Division of Water Resources runs the subsurface sewage disposal programme statewide, except in a handful of counties with delegated local programmes. Fees typically run $200 to $600, with a turnaround of about 2–6 weeks. A soil evaluation or percolation test is required before a permit is issued.
How much does a septic system cost in Tennessee?
A conventional system for a three-bedroom home typically runs $6,000 to $17,000 installed. Soil quality moves this more than anything else — on tight clay requiring a mound, budget two to three times the low end.
How far must a Tennessee drainfield be from a well?
100 feet from a private water well, with the septic tank itself allowed at 50 feet. Local rules can be stricter.
Sources
Every figure on this page traces to one of these documents.
- Tenn. Comp. R. & Regs. 0400-48-01-.08 — Septic Tank Capacity · verified 2026-09-18
- Tenn. Comp. R. & Regs. 0400-48-01 — Regulations to Govern Subsurface Sewage Disposal Systems · verified 2026-09-18