Septic System Types Guide: Conventional Gravity, Mound, ATU, and Drip Irrigation
A practical reference guide to the four major types of septic systems your technicians will encounter: conventional gravity, mound systems, aerobic treatment units, and drip irrigation systems.
Why System Type Knowledge Matters for Service Companies
Not all septic systems require the same service, the same inspection procedure, or the same troubleshooting approach. Technicians who understand the fundamental differences between system types arrive at each job with the right expectations and complete the service correctly on the first visit. For a company managing hundreds of customer accounts, understanding the mix of system types in your service area also drives equipment and training decisions.
Conventional Gravity Systems
The most common type in North America. Wastewater flows by gravity from the house through the septic tank (where solids settle and anaerobic bacteria treat the liquid), then to a distribution box, and from there through perforated pipe laterals in the drainfield. Effluent percolates down through the soil for final treatment before reaching groundwater.
Conventional gravity systems require adequate soil permeability (demonstrated by a perc test during permitting) and sufficient depth to seasonal high water table. They have no mechanical components in the drainfield, which makes them durable and low-maintenance when properly designed and sized. Standard service is periodic pump-out. Inspection involves tank, D-box, and visual drainfield assessment.
Mound Systems
Mound systems are elevated drainfields constructed above the natural soil surface, used on sites where soil depth to restrictive layer or seasonal high water table is insufficient for a conventional gravity drainfield. A pump chamber lifts effluent from the septic tank to the elevated mound bed where it distributes through a pressurized lateral network.
Mound systems have a pump chamber that requires maintenance: pump inspection, float switch testing, and alarm testing at regular intervals. The pump chamber should be pumped separately from the septic tank. Inspect the mound surface for surfacing effluent, erosion, or structural integrity issues. Vegetation management on the mound is important; deep-rooted plants can damage the drainfield.
Aerobic Treatment Units (ATUs)
ATUs use mechanical aeration to provide aerobic bacterial treatment, producing a higher-quality effluent than conventional septic systems. They are used in areas where soil conditions or proximity to water supply wells require advanced treatment. ATUs have more mechanical components than gravity systems: an air compressor or blower, a motor, floats, and sometimes an ultraviolet disinfection unit or chlorination system.
ATU maintenance contracts are standard in most states because aerobic systems require periodic inspections to verify the blower is operational, the system is treating adequately, and the disinfection system (chlorine tablets or UV) is functioning. In many states, ATU maintenance by a licensed provider is required by the operating permit. This creates a significant opportunity for service companies to build ATU maintenance contract programs.
Drip Irrigation Septic Systems
Drip irrigation septic systems deliver highly treated effluent through a network of small-diameter tubing with emitters directly to the root zone of the soil at shallow depth. They allow installation on sites with very shallow soil or challenging terrain where other drainfield types are not feasible. They require advanced treatment (usually ATU-level) before the drip field and have filters that require regular cleaning to prevent emitter clogging.
Drip systems have the most components and the most maintenance requirements of the major system types. Pump chambers, filter systems, pressure regulators, and the emitter network all require periodic inspection and service. Technicians unfamiliar with drip systems should receive specific training before servicing them.
Record system type for every customer in SepticMind so that the appropriate inspection checklist, maintenance frequency, and service documentation is applied to each account automatically.
Sources and Further Reading
- • U.S. Environmental Protection Agency - Provides comprehensive guidance on septic system types, design standards, and regulatory requirements for onsite wastewater treatment systems
- • National Association of Wastewater Technicians - Offers technical training materials and best practices for installation, maintenance, and troubleshooting of various septic system configurations
- • University of Minnesota Extension - Publishes detailed educational resources on septic system selection, soil suitability assessments, and performance comparisons between different treatment technologies
- • National Small Flows Clearinghouse - Maintains technical databases and case studies on alternative septic systems including mound systems, aerobic treatment units, and advanced distribution methods
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