Septic System Types Compared: Conventional, Aerobic, Mound and More
Short answer: Most homes use a conventional tank-and-drainfield system. Where the soil, lot size or water table won't support that, an aerobic treatment unit, mound system, or another EPA-recognized design is used instead.
Conventional system
A septic tank plus a trench or bed drainfield. This is the most common and generally least expensive design, and it works well for single-family homes on a lot with adequate soil and space.
Chamber system
A gravel-free design using connected chambers where wastewater contacts the soil for treatment. It suits areas with high groundwater, limited local gravel supply, or variable water use.
Aerobic treatment unit (ATU)
Injects oxygen into the treatment tank to boost bacterial activity and improve nutrient removal. Used on small lots, in poor soil, where the water table is high, or near sensitive water bodies. ATUs need more active maintenance than a conventional system, commonly professional inspection every few months.
Mound system
Builds a sand mound to hold the drainfield above grade, for sites with shallow soil, high groundwater or shallow bedrock. Mound systems need more space and more upkeep than a conventional system.
Drip distribution system
Disperses effluent through shallow soil layers, 6 to 12 inches deep, without a large mound. It suits smaller lots but needs electrical power and more maintenance.
Sand filter and other advanced treatment systems
Pumps effluent through a sand-filled filter for a higher level of treatment, useful where the water table is high or the site is near a water body. These systems cost more than a conventional design.
Sources
Checked July 2026.