100% Independent — Not a Contractor
location_on Sevier fee schedule confirmed · Knox, Blount, Hamilton pending
EAST TENNESSEE SEPTIC FIELD GUIDE
Independent cost data & soil-specific estimates
SYSTEM CLASSES I–V // WHAT EACH ONE COSTS
verified RANGES, NOT QUOTES

Septic System Classes & What Decides Them

The five system types your site might be allowed, what each costs installed in East Tennessee, and the TDEC installer permit the contractor has to hold for it. Your soil chooses the class; you don’t.

CASE // CLASS IV: THE ENGINEERED MOUND
WHEN THE SOIL OVER ROCK OR THE WATER TABLE IS TOO SHALLOW
Illustration of an engineered mound septic system under construction, showing the sand fill, stone bed and distribution pipes
ILLUSTRATION: MOUND UNDER CONSTRUCTION NOT A PHOTO
LAYER 01 IMPORTED SAND FILL
LAYER 02 WASHED STONE BED
LAYER 03 PUMP-DOSED PIPES
LAYER 04 FILTER FABRIC
LAYER 05 SEEDED SOIL CAP
01. Sand fill Imported

Clean sand brought in and placed on the prepared ground. It is the treatment layer the site lacks — the reason a mound needs trucks, and the reason it costs roughly double a conventional field.

02. Stone bed Washed

A bed of washed stone in the sand holds the pipes and spreads the dose. Dirty stone clogs the sand, which is one of the things the inspector checks before it is covered.

03. Pressure pipes Pump-dosed

Small perforated pipes fed by a pump so the whole bed gets an even dose. The pump adds electricity and a replacement cost ($800–1,400) that a gravity system does not have.

04. Filter fabric Geotextile

A fabric over the stone keeps soil from washing down into it while letting the bed breathe.

05. Soil cap Seeded

Topsoil over the whole mound, shaped to shed rain and seeded so it holds. This is the “built above grade” part you see in the yard.

warning Before any quote Ask who is doing the perc test and what it costs ($300–800).
SYSTEM CLASSES I – V, WITH 2026 RANGES Installed ranges for East Tennessee. Which class you are allowed is set by the soil evaluation, then confirmed by the county.
Ranges, not quotes
DESIGNATION

Class I: Conventional Gravity

TDEC Tier 1
Complete system $12,000–20,000
Field only $5,000–15,000
When it fits SOIL DRAINS WELL
Installer permit TDEC $200
check_box Soil passed a perc test; effluent moves to the field by gravity alone.
check_box Tank sized by bedroom count: 1,000 gallons for two or three, 1,250 for four, 1,500 for five or more.
check_box The cheapest design and the one you want the soil test to confirm.
CAPITAL INTENSITY LOW ($12,000 – $20,000)
DESIGNATION

Class II: Gravelless Chambers

TDEC Tier 1
Complete system NOT CONFIRMED
Field only $7,000–18,000
When it fits CONVENTIONAL SITES
Installer permit TDEC $200
check_box Plastic arch chambers replace the gravel in a conventional trench.
check_box We have a confirmed range for the field alone but not for the complete system; ask for tank and field quoted separately.
check_box Same soil requirements as a conventional gravity field.
CAPITAL INTENSITY LOW–MODERATE (FIELD $7,000 – $18,000)
DESIGNATION

Class III: Low-Pressure Pipe (LPP)

TDEC Tier 2
Complete system $15,000–25,000
Field only ASK
When it fits SLOW CLAY
Installer permit TDEC +$100 ALT
check_box Clay that absorbs too slowly for gravity; a pump doses effluent evenly across the field.
check_box Needs electricity and a pump that will eventually be replaced ($800–1,400).
check_box The installer must hold the alternative-system endorsement for LPP, not just the conventional permit.
CAPITAL INTENSITY MODERATE ($15,000 – $25,000)
DESIGNATION

Class IV: Engineered Mound

TDEC Engr. Review
Complete system $20,000–35,000
Field only $15,000–30,000
When it fits SHALLOW ROCK / WATER
Installer permit TDEC +$100 ALT
warning Not enough soil above rock or the water table, so the field is built above grade in imported sand.
check_box Solves the shallow-bedrock lots common in Sevier, Knox and Blount counties.
check_box Dosed by a pump; roughly double the cost of a conventional field.
CAPITAL INTENSITY HIGH ($20,000 – $35,000)
DESIGNATION

Class V: ATU + Drip Dispersal

Advanced Treatment
Complete system $18,000–30,000
Field only ASK
When it fits TIGHT SITE / POOR SOIL
Installer permit TDEC +$100 ALT
check_box A powered aerobic unit treats effluent before it reaches the ground.
check_box Needs electricity and an ongoing service contract — budget for it.
check_box Often the only option on small lots or where the soil will not take a field.
CAPITAL INTENSITY HIGH ($18,000 – $30,000)
rule Tank size is set by bedrooms

Tennessee sets the minimum tank by bedroom count, not bathrooms, because bedrooms predict occupancy. A contractor who sizes below the minimum fails inspection.

2 BEDROOMS 1,000 GALLONS
3 BEDROOMS 1,000 GALLONS
4 BEDROOMS 1,250 GALLONS
5 OR MORE 1,500+ GALLONS
Estimate your job arrow_forward
BEFORE AND DURING THE JOB

What has to happen, and what should stop you

gavel No cover before inspection
verified Things that must be true before you sign
01
Soil evaluated first A perc test ($300–800) or soil map exists and every quote names the system type it points to. Otherwise you are comparing guesses.
02
Permit issued before digging The county construction permit is in hand before anything is dug. Approval after the fact is not available; the fix can mean excavating a finished system.
03
Tank sized to the bedroom count 1,000 gallons for two or three bedrooms, 1,250 for four, 1,500 for five or more. This is a state minimum, not a negotiation.
04
Installer holds the right TDEC permit $200 for conventional systems, plus $100 for each alternative type. A mound needs the alternative endorsement; ask to see the permit before signing.
report Red flags (walk away, or get another quote)
ERR.01
Backfilled before inspection Nothing gets covered until the county inspector has seen it. In Sevier a failed inspection means a $100 Re-Inspection Application and a morning call to reschedule.
ERR.02
The wrong permit filed A repair permit is $75 in Sevier; a new-system permit is $300. Contractors sometimes file the expensive one because it is simpler. Ask which went in, and why.
ERR.03
A lump sum with no system type A conventional field is $5,000–15,000; a mound field $15,000–30,000. If the type is not written down you do not know which one you are buying.
ERR.04
Permit does not match the system If the site needs a mound and the installer only holds the conventional TDEC permit, they cannot legally build it. Match the permit to the system your soil requires.
Confirmed county fee schedule

Sevier County is confirmed against the county’s own figures. Knox, Blount and Hamilton show the statewide range until we confirm them.

assignment County permit pages