Septic Tank Condition
Inspect, Repair, or Re-Use Concrete Septic Tanks
SEPTIC TANKS, CONCRETE - CONTENTS: Characteristics of concrete septic tanks. Guide to the properties of different types of septic tanks: steel septic tanks, concrete septic tanks, fiberglass septic tanks, home made septic tanks - definitions and characteristics of various types of septic tanks
POST a QUESTION or READ FAQs about concrete septic tanks: special problems, inspection, installation, troubleshooting, repairs, age, durability
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Check the condition of a concrete septic tank:
This document describes how to inspect the condition of a septic tank, providing special
considerations for inspecting concrete septic tanks. Inspecting concrete septic tanks is a key component in
onsite wastewater disposal systems.
Guide to Concrete Septic Tanks: properties, sizes, installation, maintenance, repair
The photo shows a round concrete septic tank cover being removed to prepare for pumping a concrete septic tank. This is a safe cover and is rated thick enough to be driven-over by a car - but we do not recommend that practice.
Of course the area is quite unsafe while the septic tank cover is off - we would not leave the tank cover off and the area unattended. Concrete septic tanks at an existing septic installation are usually viable, but might have damaged baffles or cracks that permit seepage of groundwater in or septic effluent out around the tank.
Cracks in concrete septic tanks: Concrete tanks can crack or sections may separate causing leaks with the result of not only improper disposal of effluent (wrong location) but also subverting an attempt at a septic loading and dye test since when the system is un-used the tank liquid levels drop abnormally. Poorly-mixed concrete may also fail from spalling. Occasionally we've seen tanks made of poor-quality concrete (insufficient portland cement) which eroded badly. If the tank outlet or absorption system have been blocked, examination of the tank interior may show that effluent is or has been above the top of the baffles (see "baffles" below) thus indicating a system failure.
The inspector may detect this condition only if there is a tank inspection port which is readily and safely accessible for before, during, and after inspection when running a loading and dye test.
Damaged or lost septic tank baffles: while concrete, properly mixed and set, is quite durable, in some concrete septic tank installations we find cracked, broken, crumbled, or even totally-lost baffles. Without proper inlet and outlet baffles the septic tank sends solids to the drainfield or soakbed, much shortening its life; baffle loss at the tank inlet can lead to a sewer line blockage and sewage backup in the home. Below we give links to septic tank baffle repair or replacement information.
Septic tank settlement: if not properly set on compacted soil, gravel, or another sound surface, a septic tank may settle or tip, causing poor operation or even leaks, blockages, broken pipes.
Lost, missing, insecure septic tank access covers: permit someone to fall into the tank, usually fatal.
Watch out: be sure to keep people away from the area of a septic tank of unknown condition or that lacks a safe secure cover.
See SEPTIC TANK COVERS
Repairing damaged or lost concrete septic tank baffles
On occasion we find that the baffles at inlet or outlet ends of a septic tank have deteriorated, usually due to poor original concrete mix, and occasionally due to mechanical damage. A lost or damaged baffle at a septic tank is asking for sewage backup into the building or the passage of solids into the drainfield - substantially shortening its life.
Besides leaks due to a crack in a concrete septic tank, we find leaks into the tank due to improperly algined or placed entry or exit piping or missing, damaged gaskets at those locations. To repair septic tank leaks
see SEPTIC TANK LEAKS.
In addition to sealing openings at tank piping and cracks or holes (described below) if your septic tank is being flooded from local groundwater or surface runoff, the flooded tank will also flood the drainfield or may cause a sewage back-up into the building. Some readers have suggested sealing the septic tank covers and access ports - but these need to be removable for service or repair, and really you may be treating the symptom, not the problem.
We agree that faced with a high cost of site drainage corrections, sealing the septic tank lid may be an appealing solution. First make sure that the flooded septic tank is due to surface runoff or groundwater, not a backing-up or failed drainfield, or you're simply fixing the wrong problem.
It makes sense to direct surface runoff away from the septic tank, or if necessary, install an intercept drain to keep ground water and surface water away from the tank.
Reparing cracks & holes in a concrete septic tank
It is possible to repair a crack or hole in a concete septic tank using concrete patching compounds and some foundation repair compounds, epoxies, and crack sealers. Key considerations are
Watch out: Safety - never enter a septic tank without special training, equipment, and assistance as gases are likely to be quickly fatal even if the tank has just been pumped and washed out
Concrete surfaces to be patched need to be clean of sewage and dirt or debris, and for some patch products, dry as well
How to Convert a Concrete Septic Tank for Other Uses
Question: convert a concrete septic tank into a room, shed, boat house or other use - East Germany
2007/10/14 I live in the former East Germany and stumbled upon your excellent website
about septic tanks.
I have a really disgusting question for you but I
I have to give you one or two sentences of context first: We live on a
deep deep in a forest which is a nature reserve and we are not allowed to
build any new structures. We are just having a biological septic system
installed which purifies waste through a series of chambers (the second of
which has special plants,...).
We were debating about whether to collapse
and fill the old huge spetic tank (about 6 feet high X 10 feet wide X 15
feet long) or whether to remove it. A friend suggested that we CONVERT it
into a room or a shed or a boat house or a wine cellar or something. At
first we laughed but now we have been wondering if that would even be
possible. It is located under our lawn which ends with a steep bank
overlooking the lake so it would be easy to access the "room" via a door
from the lake side.
So my question is whether you think that it would be
possible to clean the old (cement) tank well enough and then treat/paint,
etc. the walls such that in the end it would be safe a healthy to actually
go in there?
I can't picture having this as a guest room "Oh yes, this is
under the lawn because it used to be the septic tank, sleep well!" but I
can imagine using it as a shed for our tools or a place to store the boats
-- Lord knows no one would steal the stuff because who would think to look
for a shed under the lawn!! I would greatly aappreciate your brief take
the idea. - Regards, Anonymous by private email
Reply: steps in cleaning and preparing a used septic tank for other purposes
Above: nearing completion in 2016, this East German concrete septic tank has been cleaned and sealed to permit re-purposing it as an underground storage facility. The concrete pillars left in place help protect against a collapse of the septic tank cover.
It sounds worth trying - but
Watch out: BE CAREFUL
Do not ever enter a septic tank, new or old - there could be fumes that
can kill you quickly
To convert a septic tank to some other storage or possibly occupancy use you'd need to be sure it is clean, safe to enter, and sound; you'll also need to be sure you are successfully keeping surface runoff or groundwater from entering the tank.
remove the tank cover
open the end of the tank facing to outdoors and downhill
power-wash the tank interior
disinfect all surfaces
coat or paint with a sealant and top coat
perhaps using a bactericide in your paint coating
direct suface runoff away from the septic tank entry or opening
provide a safe easy means of entry and exit
If the costs of all of these steps, including probably adding additional
windows for light and ventilation make all of this worth the trouble it's
worth considering. But I wonder if it wouldn't be less costly to collapse
and remove the remains of the tank and build something a bit larger and
Any mistake could certainly make someone sick so be thorough.
You could probably take some bacterial sample swabs from the interior
surfaces and have them checked for bacterial level by a local lab to be
sure the surfaces are safe.
Let me know what happens, and send along photos if you try this project - I
may be able to make other suggestions.
Reader follow-up: 2007/10/22
Since writing to you I had been considering removing the old tank and replacing it with a new one (basically, the same suggestion you made). We'll look into costs of getting or building something new (and maybe a little bigger) and of doing the steps you suggested and then decide. It won't be until Spring and I will write again and let you know what we do (including photos). Once again, I very much appreciate your taking your time to advice!
Reader follow-up: 2009/10/02 Septic tank converted to outdoor storage space
Maybe you remember me. I wrote to you almost 2 years ago to ask for your opinion about the idea of converting a large septic tank into a storage cellar and you kindly replied with some suggestions.
Well here we are 2 years later and fairly close to completion and at this point I am thinking and feeling that this was a good idea after all!
The new biological septic tank was up and running last summer so the old septic tank was empty over the winter. A few months ago, we took the dirt off part of the top of it to figure out exactly how big it actually is and thus access the feasibility of the conversion. It is pretty large but positioned in a way that made uncovering half of the roof and later accessing it via a door and spiral staircase -- not hard.
So, we decided to proceed. As the tank was emptied last summer when we switched to the new system, it did not smell bad. The sanitation guys came and power cleaned it well and measured the gasses with their meters and found zero bad gasses. It was baking sunny hot for several weeks and we left the tank open so it could thoroughly air out.
The sanitation guys here said that it takes 30 days to be sure that all bacteria are dead. It's been open and empty a lot longer than that now. (I will still probably take a culture to a lab at the end before we start really going down there and touching the walls, etc.).
Next, we removed the interior walls with the exception of the support posts and a 20" cross in the middle that further support the support posts and keep them from shifting. That's where we are now. It is really a good size now that I see it = The ceiling is a generous 7 feet up and it is (round) just over 12 feet in diameter.
We plan to use it to store all our annoying stuff like extra fence materials and garden tools, as well as possibly for a small wine cellar. Our East German friends (who were very used to creatively improvising and rigging things to work with odd materials and strange substitutions -- under the old East German system) have lots of ideantergarden s and advice -- like, for example, using it as a refrigerator. Anyways, it was one of these guys who suggested converting it to begin with so I am more than happy to listen to their ideas!
Last steps [ in septic tank conversion to occupied use ] now are to
1. install the spiral staircase along the wall and -- my husband's idea -- a PULLEY system for lowering and raising heavy items and to
2. paint it with a sealant and
3. add the walls over the opening and the access door with roof. Plus electricity.
I am attaching a few photos, as promised. First (9744) there is one that shows how the tank is positioned vis a vis the lawn and the driveway and the lake, etc. Then (9746) you can see what the internal structure looked like at first. In photo 1842, you can see what it looks like with the internal walls removed but the support pillars left in place (in this photo, they are just shortening the cement cross in the middle of the structure so that it is just about 20" high instead of the 5 feet it was originally.
It is now perfectly easy to get around and bright enough and airy enough not to be horrible. Of course, the wall and door will eliminate a lot of the light and airiness but we are going to usé a transparent roofing material like wintergarden plastic or something.
All in all, it will have cost about 2500. for all the work (cleaning, knocking down the walls and installing the stairs and walls, etc.) and materials (paint/sealant and cement and wood and plastic whatever for the external walls/roof.
Removing this thing would have been cost-prohibitive and it would not have been possible to install something any bigger since we are talking about a space that is under our lawn!
Also, the nature preserve laws prohibit building something new.
So, I just wanted to follow-up as promised and send you some photos with an update. Thanks for your suggestions and well, now you know,.... not that I imagine that you will have hundreds of US customers wanting to follow-suit but with the current economic crisis,... who knows! I'll send you a final photo when the fence and door and roof are built and the interior is painted and all pristine looking, if you are interested.
Reader follow-up: 2016/06/02
I just happened upon your email from some years ago.
Maybe you remember me: I live in Germany and converted my old septic tank into a storage cellar.
I'm not sure if this email is still good for you but if you reply, I would be happy to send you a brief update and photos. We are glad we did this.
Yes please do send along photos - as we've heard from several readers who have considered making alternative use of old septic tanks or other old concrete, fiberglass, or plastic structures.
Reader follow-up on conversion of an East Germany septic tank to usable space: 2016/06/04
We just put an electric cable in so we can have an outlet, a light and an electric ladder. And we are just fixing the door. Should be done with these things next week or so.
Update since 2009:
We do a lot of natural building using cob (sand, clay and straw) and earthen plasters so, last year, we put a bright tan earthen plaster over the old tar walls and ceiling. It looked great for a few days but was very quickly covered with grey and black mold. So I ordered a wonderful natural product from the US called LimePrime which immediately eliminates and prevents all mold. So now it smells super fresh and is bright white.
Poured a new cement floor.
Installed a ladder with a platform that rolls up or down (this has a hand crank but we want to replace It with an electric motor).
Built cement walls around the opening and an aluminum entrance (not sure what this type of door is called in English.
Maybe I will send a few photos today and some after the final finishes.
- Anon. 2016/06/04
Update: 2016/07/18: below is the cleaned, sealed interior of this concrete septic tank converted to an underground storage facility:
Below: seen from above-grond is a diamond-plate hinged cover assembly providing access to the underground storage facility converted from the re-purposed septic tank. Remaining tasks include installation of gas charged lift supports to make opening the access cover easy and safe, and perhaps a security lock to keep the underground storage room child-safe.
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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.
Onsite Wastewater Disposal Books
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 wastewater 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 buy 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 priced 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.
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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.
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