Indiana septic tank sizes
The short version: Indiana requires a septic tank of at least 750 gallons below the water line for up to two bedrooms, 1,000 for three, 1,250 for four and 1,500 for five, plus 300 gallons per extra bedroom.[1]
The rule
Indiana’s rule for residential on-site sewage systems, 410 IAC 6-8.3, sets a minimum septic tank capacity below the water line according to the number of bedrooms in the dwelling. Section 60, Table III, requires 750 gallons for two bedrooms or fewer, 1,000 for three, 1,250 for four, 1,500 for five, and 1,500 gallons plus 300 for each bedroom over five.[1][2] The same section requires tanks to be watertight and made of durable material such as concrete, fiberglass, polyethylene or polypropylene, protected from corrosion, and prohibits cast-in-place concrete, concrete block, wood and metal tanks.[1]
Table and catalog
Pump Professionals’ septic tank listings, which it says are available in Indiana and parts of Ohio and Illinois, include three complete Infiltrator tanks: the IM-540 (500 gallons, $718.00), the CM-1060 (1,000 gallons, $1,124.00) and the IM-1530 (1,500 gallons, $1,854.00).[3] The table pairs each bedroom count with the smallest of those tanks whose nominal size meets the minimum.
| Bedrooms | Minimum capacity (gal) | Smallest listed tank meeting it | Listed price |
|---|---|---|---|
| 2 or fewer | 750 | CM-1060, 1,000 gal | $1,124.00 |
| 3 | 1,000 | CM-1060, 1,000 gal | $1,124.00 |
| 4 | 1,250 | IM-1530, 1,500 gal | $1,854.00 |
| 5 | 1,500 | IM-1530, 1,500 gal | $1,854.00 |
| 6 | 1,800 | none listed | — |
| 7 | 2,100 | none listed | — |
Minimums from Table III; tanks and prices from the supplier’s listing; pairing by this reference.[1][3]
Read with care
- The rule counts capacity below the water line, while the listings give a nominal size. A tank’s liquid capacity can be below its nominal size, so the manufacturer’s figure should be checked.[1][4]
- “Bedroom” has a legal definition: a room of 70 square feet or more with an operable window or exterior door for egress (and, in new construction, a closet), or a room declared for sleeping by recorded affidavit.[2]
- A jetted bathtub holding more than 125 gallons counts as an extra bedroom for sizing.[2]
- The 500-gallon IM-540 is described by the supplier as a septic or pump tank; at 500 gallons it is below every Table III minimum for a septic tank, so its use would be as a pump or dosing tank where a design calls for one.[3][1]
- Every installation needs a construction permit from the local health department, which approves the design.[2][5]
Why tank size matters
A septic tank works by holding wastewater long enough for solids to settle as sludge and for fats to float as scum, so that clearer effluent passes to the drain field. A bigger tank holds wastewater longer and stores more sludge between pump-outs.[6][7] The EPA says household septic tanks are typically pumped every three to five years and should be inspected at least every three years; systems with pumps, floats or other mechanical parts should generally be inspected once a year.[8]
Larger homes
A six-bedroom home needs 1,800 gallons and a seven-bedroom home 2,100.[1] No single tank of that size was listed, so a design would call for a larger tank from another source or tanks in series where the local health department allows it; this reference does not advise on design.
Download
The table is available as indiana-septic-tank-minimums.csv.[1]
Common questions
What size septic tank does a 3-bedroom house need in Indiana?
At least 1,000 gallons below the water line under 410 IAC 6-8.3-60.
What about 4 bedrooms?
1,250 gallons.
Can a septic tank be metal or concrete block in Indiana?
No. Cast-in-place concrete, concrete block, wood and metal tanks are prohibited.
Related entries
Endnotes
- ^ a b c d e f g h 410 IAC 6-8.3-60, Septic tanks: general requirements (Table III). Indiana Administrative Code, via Legal Information Institute. Retrieved 9 November 2026.
- ^ a b c d 410 IAC 6-8.3, Residential on-site sewage systems (rule text as published 28 March 2024). Indiana Department of Health. Retrieved 9 November 2026.
- ^ a b c Septic tank (category listing). Pump Professionals (pumpprofessionals.com). Retrieved 9 November 2026.
- ^ Infiltrator Water Technologies (manufacturer site). Infiltrator Water Technologies. Retrieved 9 November 2026.
- ^ On-site sewage systems program. Indiana Department of Health. Retrieved 9 November 2026.
- ^ Septic tank. Wikipedia. Retrieved 9 November 2026.
- ^ Septic systems (SepticSmart). U.S. EPA. Retrieved 9 November 2026.
- ^ How to care for your septic system. U.S. EPA. Retrieved 9 November 2026.