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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.
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
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.
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.
Failures & operating or maintenance difficulties with Aerobic Septic Systems or ATUs
Question: Having an ATU installed, worried.
I am having an ATU unit installed tomorrow. Against my better judgment, but due to wonderful regulations, that was the plan the engineer said we HAVE to have. Total install for a 500 gallon trash tank, 1000 gallon septic tank, ATU, 176 feet of drainfield piping with Q36 equalizer is $18,519. Just in case anyone was wondering. - Steve Woodward 10/4/2011
Question: ATU performance query
Steve, how is your ATU unit working so far? Was this a replacement for a failed system? How many people in household for that size. I'm guessing 5 to 6? Are you in the North and if so did you insulate the unit for winter? How big is your lot? Lastly, did you also have a well?
Question: has trouble getting maintenance on Aerobic Treatment Unit ATU
I HAVE LIVED IN MY HOUSE ONLY ONE AND A HALF YEARS AND I HAVE HAD NOTHING BUT TROUBLE MAINTANCE PEOPLE OUT MONTHLY COSTING ALOT OG MONEY I DO NOT HAVE I THINK THIS THIS THING IS STUPID! - Michelle 4/16/2012
Michele, I'm so sorry to read about your difficulty with an aerobic septic system. In fact aerobic treatment units can function to a very high level of treatment of sewage, but indeed independent research about various types of septic system failures confirms that most often, when there are failures in advanced systems and designs, it's because of lack of or improper maintenance.
We could argue that the problem is you haven't found the right maintenance contractor, and certainly that's what needs your attention. But it is fair to say that an innate problem with the design of some systems in just about any field (computers to zone valves) is that some designs, by their complexity, have trouble finding people who will install and maintain them properly - it could be lodged as a complaint against the designer as well.
Good design of any system includes making it easy to maintain it.
Question: complaints about ATUs & ATU Aerator pump problems, costs, frequency
Stay away from these units with a 10 foot pole, they may work fine if you have 3 people or less in your household, however, that is not guaranteed. They are not designed for family usage. This is the greatest nightmare of my home purchase from 2006, worse than being underwater on your mortgage.
When it rains your toilets don't flush. You have to have it pumped once or twice a year at at rate of $250.00 each time, also, in Florida, you are required to pay a septic maintenance company $200.00 every year, plus $100.00 for a two year permit from the Health Department. Sooner or later everyone will have to acknowledge these systems are a failure. Charlotte County, Florida got rid of their mandate that all new residences install these units for a reason. They were also installing these systems on properties without enough room for a big enough drain field during the housing boom. Do yourself a favor and stay away from these things.
Concerning the above stating the failure is only due to improper maintenance is simply not true, with all respect! I have lived in my home with an ATU since 2006, it has been a pure nightmare, waiting for my county to sewer up my street, slowly they will get to me. Older septic systems last much longer and do not require so much $$ in maintenance. Either have a sewer or an older septic system, but not an ATU. This was confirmed by the very owner of the septic company that installed my system. She told me they are a life changing headache! - guest 6/27/2012
The aerator pump in my ATU causes so much turbulence in the tank that it stirs the contents in each baffled chamber in the tank and this causes solid particles to flow into the drain field array. This has caused blockages and back ups which require Roto-Rooter style cleaning at the cost of $535.00 per visit.
Three times in 5 years. ATUs are a design nightmare and any county or municipality which requires them should be investigated. In my opinion there is not enough bang for your buck here when you consider the prohibitive cost. As far as the purity the ATU is supposed to give, it is way over-rated and is overkill. The old style systems have been working fine for years. When was the last time that a cholera or dysentery epidemic occurred because of a non-ATU style system? - George Kachmar 6/27/2012
Guest, and George, thanks for sharing your views about Aerobic septic treatment units. Reports of actual user experience are very very valuable as they bring "real world" considerations and experience in to balance with "theory".
Aerobic treatment units are very widely used in some areas, such as parts of Texas. I imagine that perhaps where there are many users there are more competent experienced service companies and people's use experience may be better.
Our own research finds that studies show that ATU systems can work to a high level of treatment - in the 90% range compared with 40% treatment in a conventional septic tank; but frequent failures of the system occur, usually traced to lack of proper maintenance.
My OPINION is that any product or system that relies on installers or users to do something that most people are not going to do is, at the end of the day, not the best design. We have to design buildings and mechanical systems for what people are going to do (or not do), not what they should do.
Question: Trouble with Clearstream ATU installed in Florida
I built my home in 2007 . I too have the nightmare known as ATU . The builders advice was to get a Clearstream ATU . One of the WORST mistakes I have ever made in my life . The pump only lasted 3 years . I have already had a circuit board go bad and now the filter housing is cracked . We also have to pay a permit fee with the state and a maintenance contract which also is expensive . Along with that is the hassle of dealing with the Health Department SURPRISE inspections . THIS IS NOTHING BUT A DISASTER . PLEASE STAY AWAY FROM THESE SYSTEMS AT ALL COST ! - Alan 3/21/2013
Alan, thank you for the report of your experience with Clearstream ATUs. Indeed surveys of septic system failures that focused on aerobic treatment units found a high failure rate, but asserted that the problem was lack of maintenance or owners not following the manufacturer's instructions. Of course if a product is designed to require maintenance that people are going to find burdensome or costly that design might be itself questioned.
Given that Clearstream will perform inspection and basic maintenance for the first two years at no charge, there wouldn't be much excuse for not having had maintenance performed and in turn I'd speculate that therefore the warranty should apply.
In the Clearstream ATU instance, can you tell us what was your experience when you went to the company to ask for assistance or advice?
If you have not done so, you can contact Clearstream, a Texas company, by calling them direct at 800-586-3656 or by writing to Clearstream at Clearstream Wastewater Systems, Inc.
4899 US Hwy 69 South
Lumberton, Texas 77657.
At ATU MAINTENANCE PROCEDURES we quote Clearstream's List of Aerobic Treatment Unit ATU Maintenance Requirements & Schedule. Can you give us any details on how working on each of these was easy or difficult?
Keep us posted - what you report will help other readers.
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Questions & answers or comments about septic effluent disinfection systems - chemicals to use and others to avoid using
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 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.
 Clearstream at Clearstream Wastewater Systems, Inc. ,
4899 US Hwy 69 South,
Lumberton, Texas 77657, Tel: 800-586-3656, Website: http://www.clearstreamsystems.com.
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.
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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). 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 I recommend for professionals--DF.
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 Manual [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)
"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
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.
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.