What is a septic system?

This article explains what a septic system is, with a brief description of how septic systems work and what are the main components of a septic tank and drainfield system. This article describes the basic function, design & care of private septic tanks & drainfields or soakaway beds.

Key articles for people unfamiliar with septic systems are listed here:

An Introduction to Septic Systems - How do Septic Systems Work?

If you don't know if your building is connected to a public sewer or a private septic system, see SEPTIC or SEWER CONNECTION?.

What is a Septic System? Or What's a Septic Tank? What's a Drainfield? How do they work?

[Click to enlarge any image]

A "septic system," also referred to as a private, on-site waste disposal system, receives waste water and solids from a building's plumbing facilities (bathrooms, kitchens, shower, laundry), treats, and then disposes of the effluent from this waste, by permitting it to absorb into soils at the property.

Wastewater or septic effluent treatment is accomplished by bacterial (and other microorganism) action in the "septic" or "treatment" tank and it is mostly accomplished by bacteria in the soil around and below the effluent absorption system, or "drain field."

This bacterial action is needed to reduce the level of pathogens in the effluent discharges from the waste system into the soil. In addition to reducing the level of pathogens and the reduction of organic waste to a combination of new cell masses, CO₂, and water, wastewater treatment removes organic matter, nitrites and nitrates, and phosphorous. In an absorption field the soil performs an additional role of filtering the septic effluent.

A bit more detail is at HOW SEPTIC SYSTEMS WORK

Where are the Septic Tank & Leachfield Usually Located on a Property & How are these components Laid-Out ?

The septic tank is usually located close to the building, perhaps just ten feet away, but on difficult sites a grinder pump may instead send wastewater to a more remote septic tank and drainfield. Incidentally, depending on where you live, the "drainfield" that absorbs & treats the final septic wastewater or effluent might be called a leachfield, leaching bed, drainage trench, soakaway bed or other terms. (Contact Us to suggest other septic system terms to include here.)

The principal components of a private on-site waste disposal system usually include the following:

Below is a simple sketch of a septic tank showing how solid waste leaving the building thorugh its main drain or wastewater piping or "sewer line" or "septic line" is retained inside the tank while liquid effluent flows to the drainfield. (Click images to see an enlarged version). Here are the main components of a septic system and a brief description of what each does:

• Wastewater Piping 
  
  connecting the building to the treatment tank conducts wastewater from toilets, sinks, tubs, showers, out to a septic tank. Wastewater from toilets is called "black water" and wastewater from sinks is called "graywater"
• A septic tank
  
   or sewage treatment tank which retains solid waste, letting liquid waste flow to an onsite disposal system.
  
  Be sure to
  see SEPTIC TANK PUMPING SCHEDULE since pumping the septic tank regularly is the single most useful thing you can do to extend the life of a septic system.
• Effluent piping 
  
  connecting and conducting clarified effluent from the treatment tank to a distribution box
• A distribution box
  
   connecting the effluent line from the tank to the absorption system or "drain field"
  
  See SEPTIC D-BOX INSTALL, LOCATE, REPAIR
• An absorption system
  
   which permits effluent to drain to soils below and some of it to evaporate to air above. There are many ways to get rid of septic effluent, described
  
  at SEPTIC SYSTEM DESIGN BASICS
  and
  
  at SEPTIC SYSTEM DESIGN ALTERNATIVES,
  or see the list and definitions given
  
  at TYPES OF SEPTIC SYSTEMS - master list
• A bio-mat 
  
  or bio-mass of pathogen-digesting bacteria which forms in soil below the absorption system. The bio-mat is what makes the wastewater sufficiently sanitary to discharge into the ground.

Many variations on this general scheme are used, depending on local climate, soil conditions, available space, economy, and available materials. Special equipment and systems may be designed for problem or difficult sites such as rocky or wet ground, permafrost, or wet tropical marshlands.

...

Continue reading  at SEPTIC INFO for HOMEOWNERS, BUYERS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• HOW SEPTIC SYSTEMS WORK
• SEPTIC SYSTEM CARE GUIDE - home
• SEPTIC TANK & SYSTEM CARE BASICS for specific advice about the septic tank
• SEPTIC TANK PUMPING SCHEDULE When, Why, How to pump the septic tank
• SEPTIC CLEARANCE DISTANCES Distances Between Septic System & Wells, Streams, Trees, etc.
• TEN STEPS to KEEP a SEPTIC SYSTEM WORKING suggestions from the U.S. EPA, edits and additions by DJF
• SEPTIC TANK & SYSTEM CARE BASICS An Engineer's View & Septic System FAQ's
• WASTEWATER TREATMENT BASICS

Suggested citation for this web page

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

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to SEPTIC SYSTEMS

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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