An Introduction to Septic Systems - the Basics
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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.
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An Introduction to Septic Systems - How do Septic Systems Work?
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:
If you don't know if your building is connected to a public sewer or a private septic system, see SEPTIC or SEWER CONNECTION?.
Readers should also See Septic Guide for Home Buyers or Owners and Septic Maintenance Repair. Other helpful but still basic articles for owners of a property with a septic system include:
What is a Septic System? Or What's a Septic Tank? What's a Drainfield? How do they work?
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. |
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" - SEPTIC D-BOX INSPECTION
- 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 Master List of Septic System Types
- 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.
Frequently Asked Questions (FAQs) about septic syste,ms
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Questions & answers or comments about home septic systems: what is a septic tank, what is a drainfield? How do septic tanks work? How do drainfields work? What are the recomended steps to clean out or maintain septic tanks and drainfields?
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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- Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.
- Manual of Septic Tank Practice, US Public Health Service's 1959.
