Arkansas · Arkansas Department of Health Rules and Regulations Pertaining to Onsite Wastewater Systems
The Arkansas Department of Health administers the program directly and licenses the designated representatives who perform soil evaluations.
Minimum tank
One to three bedroom dwelling.
Design flow
Held two days for settling.
Cost index
Regional labour and permits.
Sets the design flow and the legal minimum.
Code sizes on bedrooms, not people.
Used to size the matching drainfield. Unsure? Sandy loam is the common default.
The Ozarks and Ouachitas in the west and north have thin soil over rock, with karst limestone creating groundwater protection concerns. The Delta in the east is flat alluvial ground with heavy clay and a high water table.
Conventional trenches in the better upland soils. Through the Delta, low-pressure pipe systems and mounds are common because clay and shallow groundwater rule out gravity fields.
| Dwelling | Design flow | Minimum tank | With disposal |
|---|---|---|---|
| 1 bedroom | 300 gpd | 1,000 gal | 1,250 gal |
| 2 bedrooms | 300 gpd | 1,000 gal | 1,250 gal |
| 3 bedrooms | 450 gpd | 1,000 gal | 1,250 gal |
| 4 bedrooms | 600 gpd | 1,250 gal | 1,500 gal |
| 5 bedrooms | 750 gpd | 1,500 gal | 1,750 gal |
Arkansas requires the soil evaluation to be conducted by a licensed Designated Representative, and the installer must also be licensed. The evaluation drives the design classification.
The state sets a floor. These Arkansas counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Benton | Northwest Arkansas growth corridor; karst limestone and thin soils |
| Washington | Fayetteville area; same karst constraints, heavy development pressure |
| Pulaski | Little Rock metro; mixed soils |
| Faulkner | Suburban growth north of Little Rock |
| Craighead | Delta county; clay and shallow water table |
A three-bedroom home at 150 gallons per bedroom produces 450 gallons per day of design flow. On sandy loam that needs roughly 750 square feet of absorption area. On clay loam it rises to about 2,250 square feet, and on clay a conventional field is usually not permitted at all. Run your own soil class through the drainfield calculator.
No statewide mandatory interval for conventional systems. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Arkansas run about 88% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Arkansas | When it applies |
|---|---|---|
| Conventional gravity | $7,900 – $14,100 | Good soil, adequate depth to water |
| Chamber system | $8,700 – $16,200 | Alternative to gravel trenches |
| Mound system | $15,000 – $29,600 | Shallow water table or thin soil |
| Aerobic treatment | $12,600 – $25,400 | Clay soil or small lots |
| Tank pump-out (service) | $280 – $570 | Every 3–5 years |
Replacing an existing system costs more than these figures — old-system removal and re-permitting add to every line. The replacement cost calculator covers that case, and the cost estimator adjusts all of the above for your bedroom count and soil.
Verify before you build. The figures above are state minimums compiled for planning, drawn from Arkansas Department of Health Rules and Regulations Pertaining to Onsite Wastewater Systems. County and health district rules routinely exceed them, code text changes, and only Arkansas Department of Health — Onsite Wastewater or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Arkansas rules every day.