Virginia · 12VAC5-610
The Virginia Department of Health writes the regulations; local health departments issue permits, and Authorized Onsite Soil Evaluators may prepare designs privately.
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.
Coastal plain sand in the east with a high water table, piedmont clay through the centre, and karst limestone plus steep slopes in the Shenandoah valley and mountains.
Conventional trenches in suitable soil. Virginia makes extensive use of alternative onsite sewage systems — drip dispersal, low pressure distribution and secondary treatment — and has a dedicated regulation for them with operation and maintenance requirements.
| 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 |
Virginia allows an Authorized Onsite Soil Evaluator, a private licensed professional, to conduct the evaluation and prepare the design in lieu of health department staff — this speeds the process considerably and is the common route. Alternative systems require an operation permit and licensed operator visits.
The state sets a floor. These Virginia counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Loudoun | Rapid growth; clay soils and large required fields |
| Fauquier | Rural residential with piedmont clay |
| Chesterfield | Richmond area development |
| Spotsylvania | Growth corridor, mixed soils |
| Rockingham | Shenandoah valley karst |
| Bedford | Smith Mountain Lake area with shoreline setbacks |
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.
Alternative onsite sewage systems require periodic operator visits and reporting under 12VAC5-613. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Virginia run about 102% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Virginia | When it applies |
|---|---|---|
| Conventional gravity | $9,200 – $16,300 | Good soil, adequate depth to water |
| Chamber system | $10,100 – $18,700 | Alternative to gravel trenches |
| Mound system | $17,500 – $34,200 | Shallow water table or thin soil |
| Aerobic treatment | $14,700 – $29,300 | Clay soil or small lots |
| Tank pump-out (service) | $330 – $660 | 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 12VAC5-610, Sewage Handling and Disposal Regulations, and 12VAC5-613 for alternative systems. County and health district rules routinely exceed them, code text changes, and only Virginia VDH — Onsite Sewage Program or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Virginia rules every day.