Septic Tank Pumping Guide: When NOT to Pump Out A Septic Tank InspectAPedia® -
When not to have the septic tank pumped?
Septic tank pumping and testing guides when buying a home
Septic tank pumping after area flooding
Questions & answers about when a septic tank should not be pumped
When is it a bad idea to pump out the septic tank? Under some conditions
pumping the tank may be unsafe, or it can lead to damage to the septic system.
Examples discussed here include pumping after a septic system has been flooded
and pumping some systems which can lead to dangerous or even a fatal collapse.
InspectAPedia offers impartial, unbiased advice without conflicts of interest.
We will block advertisements which we discover or readers inform us are associated with bad business practices,
false-advertising, or junk science. Our contact info is at
InspectAPedia.com/Contact.htm.
For a septic tank pumping table and explanation of
when septic tanks (onsite sewage disposal system holding tanks) should indeed be pumped
and related information readers should see PUMPING FREQUENCY. For an explanation of the meaning of sewage levels in the septic tank and how that information informs septic tank pumping frequency, see SEWAGE LEVELS in SEPTIC TANKS.
Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted. No warranties are expressed or implied. Use of this information at other websites, in books or pamphlets for sale is reserved
to the author. Technical review by industry experts has been performed and is ongoing - reviewers are listed at "References."
This article is part of our series:
Inspecting, Testing, & Maintaining Residential Septic Systems.
Also see Diagnosing Clogged Drains Is it a blocked drain or the septic system?
If you can't find your septic tank see How to Find The Septic Tank - tips on locating septic tanks for inspection and septic tank pumping.
When the Septic System is Flooded Don't Pump It Out
If you property has been flooded by rising water such as from a storm, hurricane, or a river overflow, pumping out a septic tank when ground waters are still flooding the area of the septic tank can lead to some unexpected problems:
If the septic tank is plastic or fiberglass, and if ground water is still high around the septic tank, the tank may actually float up out of the ground, leading to damaged septic piping and more costly repairs. Wait until floodwaters and ground waters have receded around the septic tank.
Even if the septic tank is concrete, if ground water is over the septic tank or even over its inlet piping or drainfield piping, if you pump out the flooded septic tank, floodwaters, including silt and mud
may simply flow into the tank, filling it with silt and debris that will need to be removed. Wait until floodwaters have receded and ground water is low enough that mud and silt and floodwater won't simply run back into the tank.
More about how to inspect, pump, and repair your septic system after flooding is at SEPTIC FLOOD RESPONSE what to do after a septic system has been exposed to flooding.
If a Septic Tank or Cesspool is Old, of Unknown or Fragile Construction Don't Pump Without Inspecting
An old, site-built septic system built of dry-laid stone or concrete block, and in particular an old home-made cesspool is at high risk of collapsing when it is pumped, or collapsing shortly thereafter. I assisted in a tragic case on Long Island, NY in which a cesspool was pumped leading
to a collapse the next day when the owner walked over the cesspool and it caved in on him. If you don't know what the septic system is made of, be sure that the septic cleaning contractor proceeds with appropriate care.
In an "unknown construction" condition, you might not even know if what's installed is a conventional septic tank and drainfield or a simple cesspool. In such cases the septic contractor should be expected to proceed with caution, perhaps pumping from high in the "tank" only a portion
of its contents, just sufficient to inspect (flashlight and mirror on a pole) the tank interior to see how it was constructed and what is its condition.
Before completing any septic pumpout or other septic repair work, be sure you have safe covers over the system(s) and any access openings. More about
septic system hazards and safe procedures is at Septic System Safety: Septic System,
Septic Tank, & Cesspool Safety Warnings for Septic Inspectors, Septic Pumpers, and Homeowners.
If the septic system sludge level is very low and the floating scum layer thickness is minimal
If the septic system sludge level is very low, perhaps just an inch or two in a 5 foot deep septic tank, and the floating scum layer thickness is also minimal, perhaps just an inch or two, the only reason I can
think of that you'd pump the tank anyway would be a need to inspect or repair it. It's quite possible to estimate the thickness of the sludge layer and scum layer using probes especially constructed for that purpose.
Measuring the septic tank scum and sludge thickness is not a normal homeowner job, and it can be unsafe (falling into tank, methane exposure, etc.) You should leave this job to a professional. How to
measure septic tank sludge thickness and floating scum layer thickness are explained and illustrated at MEASURE SCUM & SLUDGE - show this
information to your septic contractor if s/he says "it can't be done".
For an explanation of the meaning of sewage levels in the septic tank and how that information informs septic tank pumping frequency, see SEWAGE LEVELS in SEPTIC TANKS.
If you're stuck, the septic contractor has already come to and insists on pumping the septic tank, or is going to charge you the tank pumping fee just to do a "look-see" then go ahead and let the contractor pump out the tank and inspect it for damage.
But be certain to ask about and notice yourself just how much sludge there was on the tank bottom, and just how thick the floating scum layer was
at the septic tank top. If these thicknesses were minimal, as I described above, then if the level of occupancy of the building is unchanged in the future, you can probably go a bit longer before the
next septic tank pumpout is required.
See our table at Septic Tank Pumping and adjust that data to suit what you've just observed. In other words, if you had five building occupants and a 1000-gallon septic tank, the table told you to pump it after two years. If you did so but there was almost no sludge or scum, you can probably go out three years, and maybe longer depending on what you see after three years.
Do Not Pump the Septic Tank Right Before a Septic Inspection and Test
The photo at left shows red septic dye ponding at the entry to a basement at a home with a septic system in total failure.
The dye would never have appeared after our 150 gallon test if the septic tank had
been pumped right before we got to the site. Rather the dye would simply have sat in the empty 1000 gallon septic tank, hiding a problem until after the septic tank was re-filled with wastewater. Here is a totally-failed septic system which was not discovered until the morning after the new owners moved into their "new" home.
When a house is being sold: often an owner or realtor will arrange for a septic tank to be pumped just before a home inspection or before a septic system inspection or septic loading and dye test.
Such a "favor" performed for the buyer is in fact preventing a valid septic inspection and test since an empty tank means the drain field can't be tested. This is a fraudulent act and should not be tolerated.
If you are purchasing a home with a septic system it would be smart to inspect and test that system before completing the purchase. Knowing the age, location, type of equipment, and condition of the septic
system can reduce (not eliminate) the chances of an expensive surprise (like a septic system that does not work), and it can reduce the chances of a dangerous site condition (like an old cesspool or tank about to collapse).
Often a building owner will, as a "favor" to the buyer, have the septic tank pumped. This is a generous and nice thing to do if the owner agrees to take this step after any onsite
septic system testing and inspection have been completed. But otherwise it may be a dirty trick.
The step taken by a building seller of pumping a septic tank right before a septic system inspection and test to be
performed before purchase of a home may sound like a nice favor but in fact there is a serious risk that the septic tank cleanout will hide a problem:
Pumping a septic tank shortly before testing prevents an actual effective test of the septic system since it produces an empty septic tank and thus subverts the system loading portion of a septic loading and dye test (water and dye are run into the septic system to look for evidence of a backup or breakout of effluent on the yard surface).
Therefore risks hiding an imminent or already existing septic system failure
Therefore risks presenting the new buyer with a costly surprise that could have been discovered before the purchase
If a building is not in active use, pumping the tank before a septic inspection and loading and dye test will prevent a valid test as the septic tank will remain empty. Pumping the septic tank at a building occupied by 3 or 4 people should
not be done within two weeks of a septic inspection and test. This (conservative) advice helps assure that the septic tank is full before the loading and dye test are begun.
If there is a readily accessible and safe septic tank access port to permit a view of the septic tank interior (one that is not buried and not too heavy for the inspector to remove) then opening this cover can permit the inspector to confirm that the septic tank is at a normal level and thus that the test to be performed is reasonable.
Questions & Answers regarding this article
Questions & answers about when a septic tank should not be pumped
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Inspecting Onsite Waste Disposal Systems class, Explaining Septic System Operation to Clients; Visual Inspection, Testing, Invasive Inspection , Evaluation, Reporting; Future Trends, Legislation
OUTSIDE SEPTIC INSPECTION - - Simple Visual Site Inspection Gives Key Information About Septic System Condition
Septic Tank Inspection Procedure - How to Inspect Septic Tanks and evaluate the septic tank condition, baffles, sludge levels, damage, evidence of septic failure, etc.
Septic Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
SPOTTING SEPTIC BREAKOUTS - Spotting Dyed Septic Effluent Breakout Outside - Where Septic Dye is Likely to Show Up During a Septic Dye
More Reading For Owners of a Home With a Septic System
Percolation Testing Manual, CNMI Division of Environmental Quality, Gualo Rai, Saipan provides an excellent English Language manual guide for soil percolation testing. Original source: www.deq.gov.mp/artdoc/Sec6art108ID255.pdf
Soil Test Pit Preparation, fact sheet, Oregon DEQ Department of Environmental Quality, original source www.deq.state.or.us/wq/pubs/factsheets/onsite/testpitprep.pdf The Oregon DEQ onsite water quality program can be contacted at 811 South Ave, Portland OR 97204, 800-452-4011 or see http://www.oregon.gov/DEQ/
Thanks to reader Michael Roth for technical link editing 6/29/09.
Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
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.
Pennsylvania State Fact Sheets relating to domestic wastewater treatment systems include
Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and
Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by
Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)
...
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.
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.
Design Manuals for Septic Systems
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 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. 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.
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
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
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.
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
Mobile View
