EPA Sketch of an aerobic septic tank design using an aspirated mixer in the treatment tankTypes of Septic Systems & Septic Designs

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Types of septic systems: onsite waste disposal system types.

This septic system design reference lists and describes all of the types of septic systems, including both conventional septic tank and drainfield systems and alternative septic system designs for difficult building sites such as wet sites, steep sites, rocky sites, limited space, bad soils with no percolation or sandy soils with too fast percolation, and other difficult site conditions.

We provide detailed articles about each alternative septic system design choice, listing its features, design requirements, inspection details, maintenance needs, product sources.

We include links to septic design engineers, advanced septic system products and septic design books and building codes. This document is a chapter provides in our Septic Systems Online Book.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Definitions of Septic System Types & Onsite Wastewater Treatment Alternative Designs

Photo of septic tank sludge and scum layer being broken up prior to septic tank cleanout.Daniel Friedman, Massachusetts Title 5 Licensed Septic System Inspector, & New York State H.I. License # 16000005303 (inception to 2008).

This document catalogs conventional and alternative septic system designs and provides links to detailed descriptions of these designs for onsite wastewater treatment.

"Septic System Alternative Designs" refers to any onsite wastewater disposal method other than the widely used conventional septic tank and leach field. In the U.S. most states require that an "alternative septic system" be designed by a professional and submitted to the local health department for approval.

Examples of advanced septic designs include aerobic septic systems, chemical, composting, incinerating & waterless toilets, evaporation-transpiration (ET) septic systems, septic media filters, greywater systems, holding tank septic systems, mound septics, raised bed septics, pressure dosing septic systems, sand bed filters, peat beds, constructed wetlands, wastewater lagoons, constructed wetlands, and septic disinfection systems.

Each of the links below presents a document with more in-depth information about each of these alternative septic system designs.

Septic Tank Types

Septic tanks are responsible for retaining solid waste in a residential onsite wastewater treatment system (septic system), and for partial treatment of sewage and septic effluent to improve its sanitation.

In a typical conventional septic tank waste water is treated to about 40% of total treatment required before discharge to the environment.

The remaining effluent treatment normally occurs in the soils around and under the drainfield or absorption system. Some more advanced or alternative-design private septic systems achieve much higher levels of treatment by oxygenation (aerobic septic systems), chemical treatment (disinfection systems), or other methods.


Septic tanks of Single vs. Multiple Compartments

More septic tank compartments means that solid waste (floating scum, settled sludge) are better-separated from septic effluent before it is discharged to a drainfield.

Below we illustrate single compartment (below left) and two-compartment (below right) septic tank designs. Image source: USDA.

Advanced treatment septic tanks may use more compartments, including a final pumping chamber, as well as other features such as aerobic systems (shown at the top of this page), media filters, or effluent filters that both improve the level of wastewater treatment and also improve the life expectancy of the absorption field or drainfield.

One compartment septic tank USDA - DJF

You may also notice that our septic tank shown above has inlet and outlet baffles constructed of concrete while the septic tank below shows an inlet baffle constructed using plastic pipe - a common repair method if septic tank baffles are damaged.

One compartment septic tank USDA - DJF

One compartment septic tank USDA - DJF

This USDA sketch of a different two-compartment septic tank design illustrates how additional compartments can help retain solid waste in the septic tank and improve the quality of wastewater discharged to the drainfield or soakaway bed or absorption bed.

Septic Tank Materials & Construction

LARGER IMAGE: of a plastic or fiberglass septic tank.

Typical septic tank materials of construction include

Basic septic system designs are discussed in the articles listed just below

Basic septic tank and drainfield systems are discussed at SEPTIC SYSTEM DESIGN BASICS.

Here are some more detailed articles about basic septic system design, installation, inspection, maintenance, cleaning or pumping, & repair.

Alternative or Advanced Septic System Design Types (for Difficult Sites)

Also see this discussion of the most common alternative septic system besides mounds or raised bed designs:

Definitions of Types of Septic Systems, Toilets, Components

Packaged Onsite Residential and Small Commercial Septic Systems


Continue reading at SEPTIC SYSTEM DESIGN SPECIFICATIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SEPTIC SYSTEM TYPES FAQs - questions and answers posted originally on this page.

Or see SEPTIC SYSTEM DESIGN ALTERNATIVES - home - list of alternative septic system design types

Or see SEPTIC SYSTEM DESIGN BASICS - home - list of basic septic system design types


Suggested citation for this web page

SEPTIC SYSTEM TYPES at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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