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AEROBIC Septic System Failure Rates & Costs InspectAPedia®  -          Aerobic Septic System ATU Failure Rates & Costs What causes the failure of aerobic septic systems? Questions & answers about failures & problems in aerobic septic systems

Aerobic septic system or aerobic treatment unit (ATU) failure rates & repair costs: this article discusses Aerobic Septic System Failure Rates & Costs.

This website provides designs and products for aerobic septic treatment units (ATUs) for onsite waste disposal, also called fine bubble aeration systems. We address aerobic septic system design, features, inspection, repair, and maintenance. Product sources are also listed.

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Aerobic Treatment Unit Failure Rates and ATU Installation & Operating Costs

Failure Rates for Aerobic Septic Systems

Some readers have written expressing concern that they've heard that ATU's have a high failure rate, "as high as 95%". That number doesn't mean much to me without more specific data, in particular, one would need to know what was meant by "failure" and what was the cause of specific failures of ATUs. Important septic system failures are the failure to adequately treat wastewater or the failure to successfully dispose of it.

ATU Failures due to lack of maintenance: In the study discussed below, while a high failure rate was reported for ATUs (where failure here means the aerobic treatment system was not treating the effluent satisfactorily), the failures were specifically linked to a lack of proper maintenance.

Every type of septic treatment system requires periodic maintenance and repair, and I expect that every septic system eventually fails and needs extensive repair or replacement. So we could put the septic system failure rate at 100%. What would be more useful would be a statement of the typical operating cost for various alternative septic treatment systems, the typical component life, and the amount and cost of ongoing maintenance that are required.

NESC, in an issue of their Pipelines magazine (Note 1), , cited a 1998 survey conducted in West Virginia which looked at Aerobic Treatment Units to evaluate the quality of their effluent discharge. 419 ATUs were tested for TSS (total suspended solids) and BOD5 (5-day biochemical oxygen demand), and 92 percent of the systems were determined to be producing unacceptable effluent discharge.

The main cause of these aerobic septic system treatment unit failures was attributed to poor or improper ATU maintenance. I suspect that homeowners, accustomed to the tradition of inattention to septic systems until they are visibly failed, simply were performing no maintenance at all. However with proper inspection and maintenance, ATU's can continue to provide effluent which has been treated better than by a conventional septic tank and drainfield.

For example, of the 419 units, only 85 were selected for chemical tests. Of the 419 units inspected, field inspectors found (by visual inspection) deficiencies in 272 units (65%). 71% of the 85 units selected for testing were found to have deficiencies.

What was particularly remarkable, while 93% of the ATU's with a visually detectable deficiency were producing unacceptable effluent output, more stunning, another 80% of the ATU's with no apparent deficiencies by visual inspection, were producing unacceptable effluent discharge! (Op. Cit., p. 43). Here is a description of the study: "Of the 419 ATUs examined, 85 were sampled for additional laboratory analyses, which included BOD, TSS, and fecal coliforms (FC).

Approximately 150 units were tested for chlorine residual and turbidity. The survey was performed by the Environmental Services and Training Division and the Environmental Microbiology Laboratory, both at West Virginia University (WVU), and six county health departments, and with assistance from the West Virginia Bureau of Public Health. The project objectives were to survey existing ATUs for proper operation and maintenance and to determine the chemical and microbiological quality of their effluents."

Installation & Operating Costs for Aerobic Treatment Units ATUs

The NESC cites several obvious components in ATU installation and operating costs. Installation costs for an ATU include the cost of the ATU installation, including excavation and electrical wiring, the cost of construction of the post processing facility such as raised bed or sand bed.

Operating costs for aerobic septic systems include electricity for the ATU compressor or air pump, annual inspection and maintenance, usually by contract with the installer, and cost of effluent disinfection if that step is used. One website, www.toolbase.org which has some nice simple summaries of types of septic systems, cites a cost of $3200. to $5000. to install an aerobic treatment unit.

This number cannot possibly be correct for a complete system installation. More likely it is referring to the aerobic treatment unit itself, the tank and aeration system. Add to these the cost of excavation and piping for the sewer line from the building, from the ATU to the absorption system, and the installation of the wastewater absorption system, and you're probably looking at two to three times that number.

It is a bit tricky trying to compare alternative septic system costs. After all, we choose a particular system because it best fits the limitations of the site. A very limited site that requires installation of an ATU and a raised bed or septic mound system to handle the effluent, such as in a rocky building site in the Northeastern U.S., may involve a total installed cost of $25,000. This troubling number cannot be compared with the probably lower cost of a conventional septic tank and drain field ($10,000) because the latter simply won't work on the site in question.

What we can say about ATUs is that if regular inspection and maintenance are not performed, the system has a good chance of not working properly.

The cost of electricity to operate the septic aeration system is likely to be trivial, perhaps $4./month. We can also say that the trash tank or primary treatment tank will require more frequent pumping than a conventional septic tank. I expect that septic tank cleaning or tank pumping cost, often $125. to $250. per pumpout depending on location and tank size and effort to access the tank, probably is more significant than the operating cost to supply electrical power to the equipment.

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Questions & answers about failures & problems in aerobic septic systems

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  AEROBIC SEPTIC SYSTEMS
    ATU Tank Sizes
    ATU Final Treatment
    ATU Certifications
    ATU Problems
    ATU Failure Rates, Costs
    ATU Maintenance Procedures
    AEROBIC Septic Disinfectants- Calcium Hypochlorite
    AEROBIC Septic Disinfectants-Pool Chlorine
    AEROBIC Septic System ATU SUPPLIERS
    AEROBIC Continuous Flow, Suspended Growth
    AEROBIC Effluent Spray Head Maintenance

• Note 1: NESC Pipelines, Summer 2005, Vol. 16., No. 3, citing an excellent, juried article: "A Survey of Home Aerobic Treatment Systems Operating in Six West Virginia Counties", Sextone, Alan et. al., Small Flows Quarterly, National Environmental Service Center, Fall, 2000, www.nesc.wvu.edu/nsfc/sfqarchiveframe.html - unfortunately the NESC online copy is illegible. Fortunately NESC permits public download of the entire SFQ issue as a PDF, which will permit you to read this excellent article. A more careful reading than the citation above by the NESC is in order.

• AEROBIC Septic System Disinfection with Calcium Hypochlorite - Use of calcium hypochlorite tablets for aerobic septic systems
• AEROBIC Septic System Disinfection with Chlorine Tablets - US EPA declares use of swimming pool chlorine tablets illegal for septic system disinfection
• AEROBIC SEPTIC SYSTEMS - A Design Alternative for Difficult Sites
• Design Alternatives for Septic Systems: Alternate Onsite Wastewater Disposal Designs for Septic Systems - design engineers, consultants, products, books for special problem situations, difficult soils, old system repairs. 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, septic disinfection systems.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Inspecting Septic Systems: Online Book, Inspection, Test, Diagnosis, Repair, & Maintenance: our Online Septic Book: Septic Testing, Loading & Dye Tests, Septic Tank Pumping, Clearances, details of onsite waste disposal system inspection, testing, repair procedures.


• Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389 (2006), Advanced Onsite Wastewater Systems Technologies. Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going for homeowners but is a text we recommend for professionals--DF.
• AEROBIC SEPTIC SYSTEMS
• Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP; Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.
• 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.

• US EPA Onsite Wastewater Treatment Systems Manua [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems, Richard J Otis, published by the US EPA. Although it's more than 20 years old, this book remains a useful reference for septic system designers. U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980)
• Eco John® Innovative Toilet Solutions, Global Inventive Industries, Fountain Valley CA, PDF, product brochure
• "International Private Sewage Disposal Code," 1995, BOCA-708-799-2300, ICBO-310-699-0541, SBCCI 205-591-1853, available from those code associations.
• "Manual of Policy, Procedures, and Guidelines for Onsite Sewage Systems," Ontario Reg. 374/81, Part VII of the Environmental Protection Act (Canada), ISBN 0-7743-7303-2, Ministry of the Environment,135 St. Clair Ave. West, Toronto Ontario M4V 1P5 Canada $24. CDN.
• Manual of Septic Tank Practice, US Public Health Service's 1959.

• Onsite Wastewater Disposal, R. J. Perkins; Quoting from Amazon: This practical book, co-published with the National Environmental Health Association, describes the step-by-step procedures needed to avoid common pitfalls in septic system technology. Valuable in matching the septic system to the site-specific conditions, this useful book will help you install a reliable system in both suitable and difficult environments. Septic tank installers, planners, state and local regulators, civil and sanitary engineers, consulting engineers, architects, homeowners, academics, and land developers will find this publication valuable.
• Onsite Wastewater Treatment Systems, Bennette D. Burks, Mary Margaret Minnis, Hogarth House 1994 - one of the best septic system books around, suffering a bit from small fonts and a weak index. (DF volunteers to serve as indexer if Burks/Minnis re-publish this very useful volume.)While it contains some material more technical than needed by homeowners, Burks/Minnis book on onsite wastewatre treatment systems a very useful reference for both property owners and septic system designers. We refer to it often. While Minnis says the best place to buty this book is at Amazon (our link at left), you can also see this book at Minnis' website at http://web page .pace.edu/MMinnisbook
  
• Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf
• Soil Percolation Tests soil perc testing guide and instructions
• Percolation Testing Manual, CNMI Division of Environmental Quality, PO Box 501304, Saipan, MP 96950
• Planting Over Septic System Component", Daniel Friedman (author/editor, InspectAPedia.com), The Innovator, Winter/Spring 2008, BCOSSA, British Columbia OnSite Sewage Association, 201-3542 Blansard St., Victoria BC V8X 1W3 Canada
• Save the Septic System - Do Not Flush These Items Down the Toilet, Daniel Friedman, InspectAPedia.com - PDF document, printable
• SEPTIC STANDARDS
• SEPTIC MAGAZINES
  
• Septic System Owner's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000 $14.95 U.S. - easy to understand, well illustrated, one of the best practical references around on septic design basics including some advanced systems; a little short on safety and maintenance. Both new and used (low priceO copies are available, and we think the authors are working on an updated edition--DF. Quoting from one of several Amazon reviews: The basics of septic systems, from underground systems and failures to what the owner can do to promote and maintain a healthy system, is revealed in an excellent guide essential for any who reside on a septic system. Rural residents receive a primer on not only the basics; but how to conduct period inspections and what to do when things go wrong. History also figures into the fine coverage.
• Test Pit Preparation for Onsite Sewage Evaluations, State of Oregon Department of Environmental Quality, Portland OR, 800 452-4011. PDF document. We recommend this excellent document that offers detail about soil perc tests, deep hole tests, safety, and septic design. Readers should also see Soil Percolation Tests and for testing an existing septic system, also see Dye Tests
• Grass is Always Greener Over the Septic Tank, Bombeck, Erma: $ 5.99; FAWCETT; MM; This septic system classic whose title helps avoid intimidating readers new to septic systems, is available new or used at very low prices. It's more entertainment than a serious "how to" book on septic systems design, maintenance, or repair. Not recommended -- DF.
  
• US EPA Onsite Wastewater Treatment Systems Manual Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm
• Water Wells and Septic Systems Handbook, R. Dodge Woodson. This book is in the upper price range, but is worth the cost for serious septic installers and designers. Quoting Amazon: Each year, thousands upon thousands of Americans install water wells and septic systems on their properties. But with a maze of codes governing their use along with a host of design requirements that ensure their functionality where can someone turn for comprehensive, one-stop guidance? Enter the Water Wells and Septic Systems Handbook from McGraw-Hill.
  Written in language any property owner can understand yet detailed enough for professionals and technical students this easy-to-use volume delivers the latest techniques and code requirements for designing, building, rehabilitating, and maintaining private water wells and septic systems. Bolstered by a wealth of informative charts, tables, and illustrations, this book delivers:
  * Current construction, maintenance, and repair methods
  * New International Private Sewage Disposal Code
  * Up-to-date standards from the American Water Works Association
  
• Wells and Septic Systems, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992. We have found this text very useful for conventional well and septic systems design and maintenance --DF. Quoting an Amazon description:Here's all the information you need to build a well or septic system yourself - and save a lot of time, money, and frustration. S. Blackwell Duncan has thoroughly revised and updated this second edition of Wells and Septic Systems to conform to current codes and requirements. He also has expanded this national bestseller to include new material on well and septic installation, water storage and distribution, water treatment, ecological considerations, and septic systems for problem building sites.
  
• The NSFC Products List has an excellent list of design manuals/modules available from their website or by telephone 800-624-8301
• Submissions welcome. send us a suggested document link or request an exchange of website links
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