Septic Tank Size Calculator
We'll show you the rough minimum tank size for your home, based on bedroom count, from the Arkansas health department rules.
Building a new home or replacing an old tank? This gives you a quick starting point before you talk with anyone. Pick your bedroom count below and you'll see the rough minimum right away.
Minimum tank size by bedrooms
These are minimum liquid capacities for a house. A five-bedroom house uses the 1,250-gallon minimum plus 250 gallons, for 1,500 gallons. A six-bedroom house adds 250 gallons again, for 1,750 gallons.
| Bedrooms | Minimum liquid capacity |
|---|---|
| 1, 2, or 3 | 1,000 gallons |
| 4 | 1,250 gallons |
| Each bedroom after 4 | Add 250 gallons |
Where these numbers come from
Rules Pertaining to Onsite Wastewater Systems, 14 CAR pt. 21, Appendix C, Minimum Capacity of Septic Tanks. The rule is listed on the Arkansas Department of Health final rules page. Reference date November 14, 2026.
- Appendix C PDF · Appendix C in the Code of Arkansas Rules
- 14 CAR § 21-901
- 14 CAR § 21-708(j)(1)
- Arkansas Department of Health onsite wastewater program
Appendix C lists 1000 gallons for 1, 2, and 3 bedrooms and 1250 gallons for 4.
Note: For each additional bedroom add 250 gallons.
COMMERCIAL: Capacity greater than or equal to a minimum 48-hour flow or in no case not less than 1000-gallon tank
From 14 CAR § 21-901: The minimum liquid capacities required in Appendix C allow for the use of standard household appliances. Garbage grinders are not recommended for standard onsite wastewater systems.
From 14 CAR § 21-708(j)(1): When dosing from a single compartment septic tank, the tank capacity shall be increased by not less than two hundred fifty (250) gallons above that specified in Appendix C of this part.
The rules do not add gallons for a garbage disposal. If a filtered pump vault sits in a single-compartment tank, add at least 250 gallons to the bedroom minimum.
This table is for a house. A business tank follows the commercial line quoted above.
Try a bedroom count
Pick the number of bedrooms, then answer the pump vault question.
Before you plan
The number above is a rough estimate, so you can picture the size before any paperwork. A licensed Designated Representative designs the system, and the Arkansas Department of Health permit sets the final tank size. The permit can call for a larger tank than the number here.
Call us about installation or pumping
Planning a new system, a replacement, or a pump-out? Call (479) 271-0058 and talk with our office. We install septic systems, and we pump them.
See septic installation and septic tank pumping.