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Septic tank size calculator
Pick the number of bedrooms. See the smallest septic tank Arkansas allows for a new system.
Arkansas rule
Minimum septic tank size in Arkansas
The Arkansas Department of Health sets the smallest septic tank allowed for a house by its number of bedrooms: 1,000 gallons for up to 3 bedrooms, then 250 gallons more for each bedroom after that.
| Bedrooms | Minimum tank |
|---|---|
| 1 to 3 | 1,000 gallons |
| 4 | 1,250 gallons |
| 5 | 1,500 gallons |
| 6 | 1,750 gallons |
| 7 | 2,000 gallons |
| 8 | 2,250 gallons |
That's the minimum for a new system. The designer can go bigger, and the tank is only half of it. The drain field is sized from the soil test, and in Garland County the soil usually decides more than the tank does.
Older homes and lake cabins may have gone in under older rules and can have smaller tanks. The county permit or an old pumping receipt shows what you really have.
Sources
- Minimum tank size by bedrooms: Arkansas Department of Health, Rules Pertaining to Onsite Wastewater Systems (2024), Appendix C (tank size), Appendix B (daily flow) and Rule 2.5 (what counts as a bedroom). The 2024 tank table prints the 1,250-gallon row as 3 bedrooms; the 2019 rule lists it as 4, which matches the rest of the table.
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