Types of Septic Systems Approved in Alabama

Quick Answer

Complete comparison for Mobile homeowners

Understanding which system types are approved by the Alabama Department of Public Health and ADEM is essential before building new or replacing an existing system. Approved types range from conventional gravity systems to advanced treatment units, each suited to different site conditions.

If you're building a new home or replacing an existing septic system in Alabama, understanding which system types are approved by the Alabama Department of Public Health (ADPH) and the Alabama Department of Environmental Management (ADEM) is essential.

State-Approved Septic System Types

1. Conventional Septic Systems

The standard three-part system consisting of a septic tank and drain field. Most common in Mobile County where soil conditions permit. Includes:

Concrete, polyethylene, or fiberglass tank
Distribution box
Drain field trenches
Soil absorption area

2. Engineered Septic Systems

Required for challenging sites in Mobile County with poor soil conditions, high water tables, or small lot sizes. These systems are custom-designed by licensed engineers.

3. Advanced Treatment Systems (ATS)

Secondary-treatment-level systems required in environmentally sensitive areas. Provides higher treatment quality before discharge.

Approved Tank Materials

Concrete: Durable, heavy, long-lasting
Polyethylene (Poly): Lightweight, corrosion-resistant, easy to install
Fiberglass: Strong, lightweight, resistant to chemicals

Mobile County-Specific Requirements

Before any septic system installation in Mobile County, a percolation test must be performed by a licensed professional. Results determine which system type your property can support.

Regulatory Bodies in Alabama

ADPH - Primary regulator for onsite sewage systems (Chapter 420-3-1)
ADEM - Environmental permitting for larger systems
Mobile County Health Department - Local enforcement
Alabama Onsite Wastewater Board (AOWB) - Licensing

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Septic System Types FAQs

What septic system types does Alabama approve?

Alabama recognizes three main types: conventional septic systems (tank and drain field, most common where soil permits), engineered septic systems (custom-designed for poor soil, high water tables, or small lots), and Advanced Treatment Systems (ATS), required in environmentally sensitive areas for higher treatment quality.

When does Mobile County require an engineered septic system instead of a conventional one?

Engineered systems are required on challenging sites with poor soil conditions, high water tables, or small lot sizes. A licensed engineer custom-designs the system for those constraints.

What tank materials are approved in Alabama?

Concrete, polyethylene, and fiberglass tanks are all approved. Concrete is durable and long-lasting, polyethylene is lightweight and corrosion-resistant, and fiberglass is strong, lightweight, and chemical-resistant.

Do I need a percolation test before installing a septic system in Mobile County?

Yes. A percolation test performed by a licensed professional is required before any installation, and the results determine which system type your property can support.

Which agencies regulate septic systems in Alabama?

The Alabama Department of Public Health (ADPH) is the primary regulator under Chapter 420-3-1, the Alabama Department of Environmental Management (ADEM) handles environmental permitting for larger systems, Mobile County Health Department handles local enforcement, and the Alabama Onsite Wastewater Board (AOWB) licenses installers.