Septic Tank or System Drain Backup due to Heavy Use or Area Flooding: Prevention Methods
BACKUP PREVENTION, SEPTIC - CONTENTS: septic system backup prevention. How to prevent septic system backups into buildings. How to prevent sewer line backups into buildings.How to diagnose and cure septic system backup problems.. Use of check valves and backflow preventers to avoid basement flooding from heavy rain or sewer line backups. How to prevent a septic backup during heavy use of a private septic system
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Septic or sewer backup prevention:
This document explains how to avoid septic system backups when heavy use of the system is anticipated and for homes connected to a municipal sewer we discuss how to prevent sewer or storm drain backups into a building during rain or heavy flooding.
Guide to Avoiding Septic Backups During Heavy System Use
I bought a home in August 2007 that uses a 2000 gallon Septic Tank. At that time, it was inspected, possibly pumped out and was in fine working order. We are a family of 4 and for us, we’ve had no problems. On occasion, we have maybe 8 people visit at a given time. We are expecting about 60-70 people over for a Birthday Party and my husband is freaking out!
He thinks the septic tank will back up into the drains if we have that many people using the toilets, over a 6 hour period. My question is: Is my husband correct in thinking that way, will the septic system back up?????? Could you PLEASE answer these questions AS SOON AS POSSIBLE?????? The party is on 04/26/08.
Why Does the Septic System Back Up During a Party?
Indeed it seems to be just the luck that we are living happily along not giving the septic tank a thought until we have a bunch of guests over for Thanksgiving, Chanukah, Christmas, or a graduation party. Why is it that at events we often see the septic system backing up?
The explanation is that a septic system that backs up during a party was already in trouble, but our usage was modest enough that we just weren't noticing it. The surge of waste water entering the septic tank cannot flow into a flooded drainfield so sewage may back up into the home, usually at the lowest plumbing fixture. Sometimes it's not the wastewater surge but someone flushing something down a toilet that blocks a drain - that's a problem that can be cleared by a plumber using a plumbing snake or drain router. But often the problem is in the septic field itself.
Here are some simple tips for avoiding a septic backup during times of surges in use such as during a party
Pump the septic tank before the party: When a septic system is otherwise in good working condition, the septic system stress created by having many people use the sinks, showers, and toilets over a short time is not so much the solid waste as the high wastewater volume in gallons. Very high water usage over a short time can flood a drainfield or septic mound which in turn could cause a septic backup. Pump the septic tank tank right before the event, or the day before. This will give some extra capacity to absorbing this high use resulting in a sudden surge in wastewater volume.
Avoid using water unnecessarily after pump out. That means don't leave running toilets un-repaired, don't leave water running unnecessarily. See Water usage for a table of typical daily residential water usage under normal conditions.
See Don't Flush for a list of things that should not be flushed into a septic system: a list of what's ok and what's not ok to put into septic tanks and building drains.Some of these can cause a system drain blockage and thus a sewage backup into the home.
Provide additional or emergency toilets when an unusually large group of people are expected at a site served only by a normal residential septic system, consider renting one or more port-a-potty toilets from a local supplier. This is an especially good idea if you already know that your septic system is old, failure prone, and/or of limited capacity.
How Much Wastewater Will Be Produced by 60 Visitors During a Party?
In the email example above where our writer assumed there would be up to 70 people visiting the home over a 6 our period, if every visitor uses the bathroom and at each use flushes a toilet twice, that'll be 120 x 4gals = 480 gallons which will be less than the septic tank can hold.
So if otherwise conserve water, we have a typical home septic tank of 1000 gallons or larger, and if we start our festival with the tank nearly empty, we're sure to protect the drainfield from flooding during the event.
If the septic system is already in good working order you should be ok.
If your drains are already backing up, especially during a time of heavy use such as with guests in the home, see SEPTIC BACKUP REPAIR.
I had a sewer backup into my home again yesterday at a basement toilet. Our main line has a sewer back-up flap [a wastewater check valve or backwater valve]. ... Is there such a thing as a soft plastic or other material filled that would take the shape of the toilet and prevent water coming back up as overflow.
Like I did with a ball of cloths, and a brick wrapped in plastic. It did the trick in an emergency, but it's not practical. - Anonymous by request.
The advantage of installing a main sewer line backup prevention valve is that this device will avoid having to plug multiple drains in the home, and the valve, basically a big check valve, is always in place - you don't have to do a thing to get it to work.
If you are having drains backup, including at the toilet, then either your main sewer line check valve is not working, or your backup is occurring (as you suspect) because water or wastewater is draining into your in-house building drain/waste/vent system before or ahead of the main sewer drain check valve. While you could install another check valve at or near the basement toilet waste line, it makes more sense to install just one such valve to protect the entire building and to make sure that one is working properly.
Stuffing a rag or any other temporary "block" into a toilet or other drains is not the best approach to this problem. Not only can it be unsanitary and a health risk in some cases, but also, who is going to stuff drains when flood conditions occur and no one is at home?
Install a Main Sewer Line Check Valve or Make Sure Installed Valves are Working
First you may want to have your main waste line backup check valve inspected -if the sewer line is backing up from the street into your home, your main sewer sewer backup valve (waste backwater valve)
or a flood guard valve is not working.
Don't Route Roof or Surface Drainage into the Sewer Piping System
Second, you should disconnect your roof drainage from the sewer piping system entirely, routing it to a nearby storm drain, or to the ground surface (at least 12 feet away from the building and to a location that drains away from the building to avoid basement flooding).
If connecting roof runoff drains to the sewer system is actually permitted in your neighborhood, try changing the drain connection to one that is downstream from your main sewer line trap and check valve.
By the way, in some communities it is illegal to rout roof runoff into the sewer piping. Doing so significantly increases the wastewater volume load on the municipal sewer treatment system so severely that during a storm the sewage treatment plant simply overflows, dumping raw sewage into nearby rivers or waterways.
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
(May 2, 2011) Anonymous said:
Thanks. This will prevent my toilets from backing up.
(July 26, 2011) Jim Mullen said:
During a recent very heavy storm and power outage, my septic tank backed up into my basement shower. It came out like a geyser. My system uses a lift station and with the pump out, the well filled up and gravity forced it back into the house. Should there be a check valve near the house? If there isn't one, any idea of the cost of installation?
Jim the backup problem you cite is all too common, and I agree that a check valve at the drain line could probably have prevented this sewage backup. The cost to install is mostly in the labor to excavate, install, and cover up, not the part itself. In a straight-forward job in an unfinished basement where the drain line is accessible without breaking up a slab, I'd guesstimate $500. or less.
Sept 26, 2011) Faith said:
Hi I need help I dont know were my septic tanc in my house how can i find it?
SEPTIC TANK, HOW TO FIND
Article link in the master index given above at More Reading
(Mar 12, 2012) Anonymous said:
will installing a check valve stop sewer gas from seeping back into the house when it rains?
It may but it won't repair the failing drainfield that may be suggested by your complaint.
(Jan 29, 2013) fran said:
my grinder pump aotp switch keeps flipping off
look for a failed check valve
(Mar 16, 2014) Anonymous said:
What do I do when my septic tank leaking from ground up
Check for a blocked line out of the septic tank or for a failed drainfield.
Inspect the tank exterior and interior to diagnose the problem; if the tank is leaking to the surface because the outlet is blocked, causing the tank to overflow, the problem is in the outlet piping or drainfield.
If the tank is leaking out of its sides or piping near the tank because of cracks or damage the tank and piping are often repairable.
Question: basement flood after sump failure
(Apr 6, 2014) moe said:
we had a flood in our basement last week due to a sump pump failure, not a septic issue. now our septic system is over flowing outside, not into the house. could the two be related? our insurance is covering the flooding. could the septic issue also be from the flooding of the basement? The septic system was pumped out last summer, so should be working correctly. we have never had a septic issue before the flood in the basement.
I suspect that there is an important relationship between the basement flood following a sump pump failure and the septic system failure you are now seeing. I tend to mis-trust coincidences. But the situation may not be quite how it appears to you - or at least as I infer from your question below.
If the basement flood had as its root cause high roof spillage, surface water runoff or groundwater levels that put so much water around the foundation that the basement flooded - a condition previously avoided by the little Dutch Boy in the Dike basement Sump pump, then those very same conditions could well have flooded a failing or poorly-designed septic drainfield or soakbed.
In turn a flooded soakbed means that the effluent has trouble leaving the septic tank.
In turn all of that means you may see sewage effluent at the ground surface anywhere outside: at the septic tank, distribution box, or drainfield, or areas near the drainfield. Worse you might be at risk of a sewage backup into the building.
You want to take a look at the Septic Tank Pumping Fantasies we discuss at
There you'll see that contrary to your surmise, pumping the septic tank out last summer, while an important step in maximizing the life of the drainfield, is itself not a shred of basis for arguing that "the septic system should be working correctly".
(Apr 26, 2014) Anonymous said:
I have a problem with my septic plugging up at the baffle. There is only about six feet from the house to the tank. Dug up the line (most of it) to see if maybe roots were attacking the live but found no roots that deep. What is happening is the clog is cylindrical at the baffle and almost looks like the clog is happening in the pipe but is pushed out to the baffle. Use to happen every month or so not about every week. Tank was pumped about 16 months ago so it should be good for another year or two. The floating scum layer is really think and hard. We use an additive for the tank so it should be in good condition. Is it possible that the scum layer is to thick already causing the intake to clog? Do you think I need to pump it again? I really do not want to spend thousands for some guy to come out and tell me the tank needs to be pumped again. I have a 2700 sq/ft house with only three people so I should last four or five years. Any help?
It's unusual for normal septic tank wastewater to clog the baffle unless there was an excess of toilet tissue or some object being flushed down the drain. More typically the waste falls into and onto the "pillow" of floating scum in the baffle area and pushes through it as needed.
But when the septic tank is pumped it's good practice to watch for that floating scum packet that's inside the baffle area to fall into and be removed from the septic tank. If it stuck and never was pumped out that could be a problem - typically solved by asking the pumper to be sure to remove it during tank pumpout.
Let me know what your septic pumping company says. In a properly sized tank it'd be a bit rapid to need to pump again after 16 months unless the building has very high occupancy
(May 16, 2015) Ryan Prough said:
We just moved into this home and it had a brand new septic system installed last year. Its been raining for a few days now and we have water seeping through the area around the septic line within our foundation. I think the field is saturated but I have no idea what to do. Its not a lot of water by any means but it is supposed to rain for another day or so. Any advice would be greatly appreciated.
What you describe is a common problem: the trench carrying the sewer line acts as a natural catch point for surface and groundwater and worse, aims it right at the foundation wall where there was a hole punched to pass through the sewer pipe itself.
1. Be sure gutters and downspouts are unclogged and are directing water away from the foundation
2. same for site grading
3. Excavate outside the wall to clean and seal around the pipe penetration
4. If necessary install an intercept drain to slope properly to take water out of the sewer line trench, away from the foundation, and down-slope to daylight. If your site won't permit that you may need to install an outdoor sump - a more troublesome arrangement.
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Thanks to reader - (Anonymous by request) for discussing alternative preventive measures to stop basement drain and toilet backup prevention - July 2010
Backwater Valve Supply Co., Akron, OH, Tel: 330.836.9393, Email: Help@Backwater-Valves.com, website www.backwater-valves.com/Backwater-Valve-Diagram.asp has a good sketch that is their basis for recommending when a sewer backup prevention valve is needed. Web search 07/10/2010 - original source: www.backwater-valves.com. Quoting from the company: Many municipal Building Codes require you to have a backwater valve if your plumbing fixtures are below the top of the first upstream manhole on your street. A properly operating backwater valve allows flow to only go in one direction (out), preventing wastewater from entering your building during regular sewer system maintenance or accidental sewer system backups. To find out if you have or need a backwater valve, check your plumbing plans or consult with your builder or a professional plumber. Remember, if sewage backs up into your home, the cost to repair damages and clean up the mess will be well high than the cost to install a valve. Laws allow that towns and municipalities cannot be held liable for damages when a backwater valve has not been installed by a property owner. Classification: Type I – intended for use in horizontal pipe runs to floor drains, building drains, sewers, holding tanks, etc.
Application: Backwater valves should be used in building drainage systems whenever a risk of flooding due to sewer surcharge, back up, or failure exists.
Backwater valves must be installed to ensure access for inspection or maintenance.
Periodic inspection is important to maintain satisfactory performance of the backwater valve.
The building owner must maintain and keep backwater valves in proper working order.
Check Valve Maintenance Guide from the City of Ann Arbor, MI. , web search 07/10/2010, original source: http://www.a2fdd.com/Documents/maintenancedoc_checkvalves.pdf
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
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.
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
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.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
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.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones