The septic system types Indiana allows

Before any construction permit is issued, and before a soil absorption system is replaced or altered, an on-site evaluation including a description of the soil profile has to be conducted. The soil is described by a soil scientist using NRCS guidelines, and the profile is recorded to a depth of five feet or until a layer is reached that cannot be read.

Source: 410 IAC 6-8.3-56(a) to (c), read 2026-08-20.

• Conventional trench field. The cheapest outcome and the one good soil supports. Effluent leaves the tank and disperses through trenches into the soil.
• Elevated sand mound. Built up above the natural grade where the water table is high or usable soil is shallow. The state publishes a standard and a design manual for these.
• Subsurface drip. Distributes small doses across a wider shallow area, which suits tight lots and difficult soils. It has its own state standard.
• Chamber trench technology. A gravelless trench system with its own published standard.
• Aerobic treatment unit. Treats effluent mechanically before dispersal, used where the soil cannot do the whole job. Indiana publishes an ATU standard.

Anything with moving parts. Where a system has components other than a septic tank that need scheduled inspection and maintenance, a county operating permit is renewed at least once every three years rather than every five, which is the rule's own way of saying these systems are not fit-and-forget.

Source: 410 IAC 6-8.3-54(a), read 2026-08-20.

Not if the soil evaluation does not support it. The permit is issued against the design, and the design is reviewed against the soil profile. A system built to a design the county did not approve is the fastest route to a correction order with a deadline on it.

Source: 410 IAC 6-8.3-55(a) and (b), read 2026-08-20.