Types of Septic Systems Approved in MS: Complete Guide for Hattiesburg Homeowners

Mississippi does not mandate a single septic system design — MDEQ approves multiple system types to address the diversity of soil conditions, lot sizes, and proximity-to-water scenarios found across the state. In Hattiesburg and the Pine Belt, soil conditions and seasonal water table variation mean that homeowners may encounter any of several system types. Understanding what you have — and why it was specified — is foundational to maintaining it correctly.

Conventional Gravity Systems

The standard tank-plus-drainfield design using gravity flow. Effluent moves from tank to distribution box to drainfield by gravity alone, with no pump required. The simplest, lowest-maintenance design and the lowest installation cost when soil conditions permit. In Hattiesburg's clay-heavy areas, conventional systems work when properly sized but require conservative loading and regular pumping.

Pressure Distribution Systems

Similar to conventional systems but using a pump to distribute effluent evenly across all drainfield zones simultaneously, rather than relying on gravity to fill zones sequentially. Pressure distribution provides more uniform soil loading, extending drainfield life in marginal soils. Common in Pine Belt areas where conventional gravity distribution would overload near zones and underload far zones due to clay's uneven percolation.

Mound Systems

An elevated drainfield constructed on imported sandy fill above native clay that fails percolation testing. Effluent is pumped to the mound's distribution network. Common throughout Forrest and Lamar County where site soils are too clay-heavy for conventional installation.

Aerobic Treatment Units (ATUs)

Multi-chamber systems that inject air to support aerobic bacterial treatment, producing significantly higher-quality effluent than conventional anaerobic systems. Specified for sites near sensitive water bodies, with minimal lot area, or with the most challenging soil conditions. Higher installation cost and ongoing maintenance contract requirement.

Sand Filter Systems

Intermittently dosed sand filter beds providing high-quality treatment before final dispersal. Appropriate for sites near surface water or with shallow soil depth. Require pump chambers and distribution networks but produce reliably high-quality effluent.