Sewage backup cause, prevention, & response:

This article series explains how to deal with and test for sewage backup contamination, sewage contamination testing, inspection, and cleanup- remediation in residential and commercial buildings. If you have had sewage back up and spill out of toilets into the building, cleanup is needed and you may face bacterial hazards.

If you have had a sewage backup or burst house drain pipe in your building this document offers some advice on how to test for sewage contamination, bacterial and viral hazards, and links to sewage spill cleanup and bacterial hazard information regarding sewage and septic spill contamination.

We explain why and how testing for sewage contamination is performed and we discuss the urgency of proper cleanup following a sewage backup or spill in a building. The photo above shows what dirt and sewage sludge may look like in a basement after a sewer line backup.

Testing For Bacterial Contamination and Cleaning Up Sewage Backups in Buildings

If your building has had a septic or sewage system backup into the structure

see SEWAGE BACKUP, WHAT TO DO

In this article we discuss how to test for bacterial or other pathogens in a building - tests that may be useful after a sewage spill cleanup in order to assure that the building is acceptably clean.

[Click to enlarge any image]

Checking buildings for indoor air quality or other contaminants which may affect occupant health should not omit inspecting and taking site history for evidence of sewage or septic system backups into the structure or basement or crawl space areas below the structure.

Gray water and black water (sewage) can cause a wide range of fungal, bacteriological, viral, and parasitic hazards in buildings.

The photo shows evidence of raw sewage overflow in the crawl space under a home. Although a new waste line was installed (the white pipe at the top of the photograph) no cleanup has been performed.

Both a one-time event and recurrent sewage leaks into a building would be aconcern, particularly if prompt and competent cleaning were not performed.

If recurrent sewage contamination has occurred more extensive building cleaning and treatment are likely to be required.

One reason that experts recommend very prompt treatment following a sewage backup in a building is the wish to avoid transmission of bacterial contamination to other building areas.

Examples of sewage bacteria and virus transmission might be by movement of people from contaminated areas to other building areas (tracking contaminated soil), and air movement of aerosolized particles or contaminated dust through the building by natural convection, heating and air conditioning equipment, or other sources of air and dust movement.

Testing for Sewage or Septic Contamination

Watch out: sewage spills contain contaminants that can cause serious illness or disease. The photograph above shows a rather innocent-looking wet concrete basement floor following a sewer line backup into this building. In fact a very high level of pathogens was present on the concrete, on the lower portions of furnishings, and on and inside the paneled wall cavity.

Demolition, cleaning, and disinfection were needed. These surfaces were then re-tested after cleaning and disinfection were complete.

Additional testing was conducted to confirm that the workers did not contaminate other building areas during this cleanup.

Disease causing agents in raw sewage include bacteria, fungi, parasites, and viruses and can cause serious illnesses including bacterial infections, Tetanus, Hepatitis A, Leptospirosis, infections by Cryptosporidium & Giardia and gastrointestinal diseases.

For a detailed list of the pathogens found in common household wastewater such as a septic tank and drainfield, see also our discussion of pathogens in sewage
see what makes up the contents of residential sewage explained

at SEWAGE PATHOGENS in SEPTIC SLUDGE.

Also see SEWAGE & SEPTIC CONTAMINANTS

While sewage may contain many pathogens harmful to building occupants, testing for this problem usually focuses on indicator organisms including total coliform, fecal coliform, Escherichia coli (E. coli), and Enterococcus as these species are expected in human sewage waste. They are potentially harmful themselves as well as serving as an indicator of sewage contamination.

How are Sewage Contamination Tests Conducted?

Sterile Swab Tests for Sewage Contamination

Typical sampling methods to test for sewage contamination in buildings include use of sterile swabs on sample surfaces both in the suspected area and as a control in other building areas where low or no contamination is expected.

Step by step details of how sterile swabs are used to collect environmental samples of suspected mold, sewage, pesticide residue, or other substances are found

at SWAB TEST KIT PROCEDURE

Swab tests for environmental sampling are also discussed at

• BLOOD in ART WORKS, TESTING FOR
• MOLD CULTURE TEST KIT VALIDITY
• PESTICIDE EXPOSURE HAZARDS
• SWAB & PCR SAMPLING & TESTS for MOLD

Bulk Sample Tests for Sewage Contamination

Bulk samples of debris or building materials may also be collected, such as drywall suspected of having been wet with a sewage backup. Samples are sent to a qualified laboratory for culture and examination for these bacteria.

Since there are a variety of tests for bacteria and for possible sewage contamination, specification of the definitive lab test for sewage contamination is important where health concerns are at stake. Be sure to review the test choices with your laboratory before ordering a specific test as test accuracy and cost vary widely.

UV Light for Spotting Sewage Contamination& Urine

We also use UV light to screen buildings for sewage contaminants, urine, or other body fluids, including blood. See

• ANIMAL or URINE ODOR SOURCE DETECTION
• BLACK LIGHT & UV LIGHT USES
• BLOOD in ART WORKS, TESTING FOR
• URINE ODOR SOURCE DETECTION

Sewage Backup & Contamination Cleaning Guidelines & Standards

This section has moved to SEWAGE CLEANUP PROCEDURES & STANDARDS

At SEWAGE & SEPTIC CONTAMINANTS we list the pathogens and contaminants commonly found in sewage and in sewage backup waters.

In this article series we explain the causes of sewer or septic backups into buildings, the health hazards, testing, and cleanup of sewage backups, and the cure or prevention of future sewage or septic backup problems.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: need help with floor odors after a sewage backup

Hello, hoping you can help guide me. I was unable to post a question to a topic page.

I had a clogged toilet that overflowed onto my laminate floor - about 1.5 inches. The liquid was cleaned and a bleach solution sprayed. But over the course of a couple of months the room started smelling musty. My son started coughing, having stuffy nose, itchy eyes.

Background: We live on an island with a low water table. Our home is circa early 1930s. The affected room is ground level - a "finished" basement. We once had carpet but earth around the room perimeter caused moisture intrusion and mold. We removed the carpet and had mold abatement. We then covered the subfloor with laminate, and poured concrete around the outside perimeter of the room to avoid further intrusion.

Last Friday, we (professionals) removed the moist laminate floor. We were then reminded that on top of the concrete subfloor is a "linoleum" tile floor on which the floating laminate was placed. A commercial dehumidifier and "scrubber" were placed in the room for 72 hours.

Toward the end of the 72 hours I passed by the window opening for the scrubber air vent and noticed what smelled like a very musty odor. I thought this was strange after 72 hours of dehumidification. The next day, the company switched out the dehumidifier, as we thought it wasn't working due to no evidence of water being pumped from the dehumidifier. Next day, still bad odor.

The project manager came out and his analysis is that the odor is not associated with moisture, but with some kind of VOC coming from the breakdown of the "linoleum." Perhaps caused by the sewage water? Perhaps from something else? Glue? (though no glue was used with the floating floor).

I am in a pickle. The company wants to test for asbestos and then remove the linoleum, assuming that that is the cause of the odor. I want to know what is causing the odor before I remove the floor.

If I have asbestos under the floor, I'd rather keep it encapsulated. I thought to test for VOCs and asbestos at the same time, but after speaking to a few different companies, thought it would be better to test the VOCs after floor removal. Now I don't know if removing the linoleum is the best course.

I hope you can help. None of the website topics quite get to the nuances of this situation.

Many thanks!!

Moderator reply: tackling your sewage backup + mold + odor + asbestos flooring hazard question

Thank you for the sewage backup, mold, odor, asbestos question - it helps us realize where we need to work on making our text more clear or more complete. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer  than we can give by email alone. You will find additional depth and detail in articles at our website. 

That said, I have these comments: 

First an apology: our comment box support on pages is provided by an independent programming company: Countable in Canada, by Clark Van Oyen and Justin Carretas  who is not always able to keep the comment box working. We've let Justin know that their server is down.

So thank you for going ahead and contacting us by email. When a situation is urgent, that's the next best way to contact us. 

1. Warning of incomplete sewage spill cleanup and incomplete mold abatement

I don't have any details of your mold abatement, but if you only looked into the layers of flooring and never inspected wall cavities I'm doubtful of its completeness.

If sewage passed under your sheet flooring and that was not removed and the exposed surfaces cleaned, the cleanup was incomplete and in my OPINION unsafe. 
When faced with costly procedures for solving any problem there is always a sore temptation for service companies to sell and building owners to buy magic bullet solutions that, unfortunately, rarely hit the target. 

A 1.5" flood is exactly the thickness of a modern 2x4 that might be found as the sill plate or "shoe" in wood-framed partition walls - so it's quite possible that water seeped up in any drywall or paneling on walls.

Spraying bleach on exposed surfaces will not treat mold- or sewage-contaminated building cavities or the under-side of layers of flooring.Spraying bleach alone is never an effective treatment for mold contamination. 

Details are at MOLD CLEANUP, BLEACH 

A sewage backup that's not properly remediated (if that is indeed the case at your building) risks leaving serious health hazards in a building.

Those details are above on this page and also

at SEWAGE CLEANUP PROCEDURES & STANDARDS - https://inspectapedia.com/hazmat/Sewage_Cleanup_Procedures.php

2. Limitations of using air scrubbers and water extractors

And water extraction never successfully dries out wall or ceiling cavities fast-enough to prevent mold contamination if those areas have been wet.

In five decades of building investigation and remedy experience I have not once found that a dehumidifier and/or air scrubber could ever be successful at cleaning and drying a flooded building when water has entered wall or floor cavities or layers or insulation. 

An air scrubber can no more remove a building mold contamination problem than can you, standing in your kitchen, wave your vacuum cleaner wand at the ceiling and suck out dust-bunnies from beneath the living-room couch.

A dehumidifier set running in room can not draw water out of closed but flooded building wall and floor cavities fast-enough to prevent mold contamination in those spaces. I've opened such cavities weeks after the event and found water still present.

3. First focus need not be on VOC s from old vinyl flooring

We would not expect a VOC problem from a very old vinyl floor. VOCs are highly volatile - hence the name. Volatile means such gases don't stick around unless there is an unusual, persistent source. And you may be confusing MVOCs (mold VOCs) and VOCs from building products. 

But if there are other materials such as laminate wood flooring or even some modern cabinetry, those can offer persistent off-gassing. 

Your focus first needs to be on completeness of the sewage backup cleanup and on the risk of hidden mold in buidling cavities.

4. Need for asbestos testing before touching old flooring?

About asbestos testing, some companies won't attempt to remove flooring that might contain asbestos without first testing for that material. That makes sense if dust-creating demolition will be needed, such as for a glued-down floor covering. 

But in fact if the flooring is sheet vinyl that is not glued-down it can usually be simply rolled-up and carried out intact - such that there is in essence no meaningful airborne asbestos hazard. 

5. Subtle and Thorough more-complete advice on finding and removing building mold after flooding and about finding sources of odors 

I recommend that you take  a look at 

HIDDEN MOLD in PANELING  https://inspectapedia.com/mold/Paneling_Mold_Contamination.php

HIDDEN MOLD in CEILING / WALL CAVITY https://inspectapedia.com/mold/Hidden-Mold-in-Ceiling-Wall.php

HIDDEN MOLD, HOW TO FIND https://inspectapedia.com/mold/Find-Hidden-Mold.php

MVOCs & MOLDY MUSTY ODORS https://inspectapedia.com/mold/MVOC_Testing.php

MVOCs & MOLDY MUSTY ODOR REMOVAL https://inspectapedia.com/mold/MVOC_Odor_Removal.php

At  ODORS GASES SMELLS, DIAGNOSIS & CURE - home, https://inspectapedia.com/odor_diagnosis/Odor-Diagnosis-Cure.php

you will find a collection of diagnostic procedures including using a smell patch test to determine the source of odors from building surfaces. But frankly from your description alone I suspect a greater hazard from incomplete sewage backup cleaning. 

Do let me know if any of those articles leave you with questions, and do let me know what you find as you further-investigate your building.

Reader follow-up: got another inspector, more thorough, better plan

Many thanks for your reply! I appreciate your response so much. It led me to trust my gut and call insurance to ask for a second opinion on what is actually going on. The company I called to come out, just didn't take the extensive measures needed to properly assess the situation. I was so focused on mold, that I didn't emphasize the server clean up. Obviously both are important, but they are supposed to be the experts, not me!

I opted to go with an insurance recommended company. Guy came out and spend an hour assessing, asking questions, measuring, photographing, etc! Said that about 6" of wall will need to be removed, as well as bathroom floor and linoleum, which he felt confident has as asbestos

. Asbestos testing taking place tomorrow. This floor is practically superglued to the concrete, so no just rolling up! He said the floor is probably off-gassing (as you noted) from the water that got between the concrete and the vinyl.

I feel much better, and feel like we have a scientific path forward :). - Anon by private email 2022/04/27

On 2020-01-03 - by (mod) - you can test soil or puddles on the surface for sewage

George

Yes you can test soil or puddles on the surface for sewage. Start by calling local water test Labs where you live is many boost Labs can also do sewage contamination testing.

On 2020-01-03 by George

I live in a low area drainage is starting to be a bad issue. Keeping getting bad run off running off other side of driveway. It is now getting dark black mud. Have spell sewage before once near property line toward neighbors side. Not want to feud with them if all possible. Is there way to have test soil for waste before I proceed to call city ?

On 2019-12-13 by (mod) - health hazards of living in a home where you are exposed to raw sewage

Sasha

If the health hazards of living in a home where you are exposed to raw sewage are not obvious to your housing authority it may be the case that there is financial aid funded by the federal government that can assist you in having the home properly cleaned and repaired (I don't know this but I found this

NATIVE AMERICAN HOUSING ASSISTANCE AND SELF-DETERMINATION ACT OF 1996 [PDF] original source:
https://www.congress.gov/104/plaws/publ330/PLAW-104publ330.pdf

otherwise you'd need local legal aid to help you in this priority order

1. assure personal safety and health for yourself and other occupants of the home: this could mean that the home is not safe to occupy so people need to be given temporary housing that is safe and sanitary

2. have the home properly repaired and cleaned so that it is safe to occupy

3. Notify your authorities both orally and in writing of immediate and serious health hazards if there is or has been sewage in the home that was not properly cleaned-up and disinfected.

Do keep me posted on what you're told; if it helps you get help you can post specifics identifying your location and authorities involved.

Sometimes letting the sun shine in on a situation can help prompt action.

On 2019-12-13 by Sasha starr

My apartment 2014 serwer backup sinks toilet tub. My tribal housing didn't get to it until 2 weeks later. I'm 8 months preggo bucketing 5 gallon buckets out of my tub to keep it from going over. When I left id get back to clean it up . Long story short recent diagnoses right side heart failure and severe pulmonary hypertension in my lungs. Housing until this day hasn't cleaned fixed nothing. My whole bathroom feels like it's gonna fall thru
Walls are mold tiles paying
Parting n cracking toilet rocks. Ive had inspections work orders nothing been done to fix
Anything ive cleaned bleached
If anything happens to me id now
Hope my kids would be taken care of

[Photo above]

On 2019-11-02 - by (mod) -

Lewis

Sorry I can't say. Certainly knowing the country and city where the 55 gallon drums of sewage are collected and handled will let you find your local health department who will know your sanitary regulations.

I speculate that there are questions of safe collection, transport, handling and also disposal all involved here.

On 2019-11-02 by Lewis

the local supervisor collects frozen honey bucket bags in 55 gallon drums and allows them to freeze, and are regularly picked up. Then the drums are brought inside the local wastewater plant to thaw, and hauled to landfill to be dumped in sewage lagoon. Is this a safe and legal practice?

On 2019-02-17 - by (mod) -

Apologies but I don't quite understand the question the way you have phrased it. If you have open sewage in your home that's a very serious contamination Hazard.

I don't understand rotting water tanks since water tanks are usually made of steel. It certainly fairly straightforward to disinfect or sanitize a well and water supply system as well as to have it tested for bacteria and other contaminants.

There also are of course procedures for testing the indoor environment and surfaces for sewage contamination.

On 2019-02-17 by Elena

How much, on a norm. Is an exposed sewage pipe containing in bacteria to a in home environment. Or what role does a rotted water tank take place in exposing bacteria

On 2018-11-30 by Tara - Can black water and coliform bacteria from a SSO contaminate groundwater

Can black water and coliform bacteria from a SSO contaminate groundwater for more than six months if the spill covered the ground surfaces? Can contamination on its own?

On 2018-11-30 by (mod) - Responding to an SSO - Sanitary Sewer Overflow or spill

Tara

(for other readers an "SSO" is defined in this context as a "Sanitary Sewer Overflow")

Outdoors soils are never bacteria-free and commonly contain both coliform and E-coliform bacteria regardless of whether or not there has been a sanitary sewer overflow.

Sanitary Sewer Overflow SSO References

• NEW ILLICIT SEWAGE DISCHARGE DETECTION AND ELIMINATION, [PDF] US EPA, retrieved 2018/11/30, original source: www3.epa.gov/region1/npdes/stormwater/presentations/20110512NHIDDE.pdf
• SEPTIC SYSTEMS AND NUTRIENTS, Michigan DOH, original source: michigan.gov/documents/deq/wrd-swas-nutrients-septic_555248_7.pdf
  available at Inspectapedia.com
• San Antonio TX, SSO REDUCTION PROGRAM, SAWS, (San Antonio Water System), original source: saws.org/infrastructure/epa/docs/20150121_SewerMgmtProgCMOMProgram_REV01.pdf
• Texas DEQ, UNAUTHORIZED DISCHARGES AND SANITARY SEWER OVERFLOWS, original source: https://www.tceq.texas.gov/assets/public/comm_exec/pubs/rg/rg-395.pdf
  Excerpts:
  
  During dry weather, the most frequent causes of UDs and SSOs are reduced capacity, blockages, malfunctioning lift stations, and vandalism.

  Grease entering the collection system is also a common contributor to dry-weather UDs and SSOs.

  It is possible to minimize dry-weather UDs and SSOs by implementing an aggressive preventive maintenance program coupled with public education.

  Local enforcement of grease-trap ordinances and pretreatment ordinances is also effective in reducing UDs and SSOs.

  During wet weather, the most frequent causes of UDs and SSOs are infiltration and inflow (I/I) into the collection system due to aging and deteriorating infrastructure.

  Infiltration is groundwater that enters the collection system through leaky pipes, faulty pipe joints, or defective manholes.

  Inflow is surface runoff that enters the collection system through missing or defective manhole covers, uncovered or damaged cleanouts, illegal stormwater connections, or defective pipes and manholes in streambeds or roadside borrow ditches.

  I/I can be confirmed by physical inspection of collection lines and manholes, smoke testing, and inspecting collection lines with cameras.

  Once problem areas are identified, a plan can be formulated to reduce I/I using systematic repair and replacement.
  

You will read in all of these documents that the FOCUS of concern is with reducing future SSOs, not on removing contaminated soil nor with duration of bacterial presence in soils.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: What follow-up inspections or tests should be done to be sure that a sewage cleanup was properly done?

2017/01/02 Jammel said:

Who do I call to come test my home to make sure it was cleaned well & it's Hazmat free after a septic backup?

I live in Inkster, MI

Reply:

Good question, Jammel

You may get free advice from your local health department,

You may be able to get a copy of tests and inspections performed by the independet expert hired by the cleanup company how did the sewage backup cleanup

You might be best served by a paid inspection and testing by an industrial hygienist or other indoor environmental expert whom you hire from your local area.

At any inspectapedia.com page top you will find a menu of links from which you should choose EXPERTS DIRECTORY to find an expert who may offer what you need.

Typically the professional will review the case history, inspect the areas where the sewage backup occurred, and the extent of work, followed by an inspection of other areas of the building. Typically swab tests are taken to allow a check for unacceptable levels of bacteria left on representative Building Services. Of course you're on site expert will have her own opinions about exactly what needs to be done.

Question: cause of basement flood after septic tank was pumped?

I had my septic tank pumped out and my basement flooded and I was wondering what could cause that? The company said it’s not related but it occurred the same day and I’ve had no problems with flooding since then. - Anonymous by private email 2019/08/09

Reply: possible causes of sewage backup soon after a septic tank is pumped

First we need to know where / how "floodwaters" entered your basement. Was it roof runoff, surface runoff, a burst water supply pipe or a sewage backup;

If it was a sewage backup and it occurred immediately after a septic tank pumpout possible causes include

• - pumper truck drove over and crushed a sewer line between house and septic tank - discover by observing ruts in yard, sewer camera inspection of the sewer pipe
• - pumping process damaged a septic tank inlet baffle or otherwise left debris that blocked sewage flow into the septic tank
• - septic tank was actually not left empty, was left full of sewage AND the septic fields are failed or blocked
• - something else less obvious

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Continue reading  at SALVAGE BUILDING CONTENTS if you need to remove and clean or salvage building contents such as clothing & furniture,or select a topic from closely-related articles below, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see SEWAGE CONTAMINATION FAQs - questions and answers about sewage contamination in or around buildings.

Or see these

Recommended Articles

• CRAWL SPACE SEWAGE CLEANUP
• GARDENS NEAR SEPTICS
• HEALTH DEPARTMENT HELP for RENTERS if your rental home has unsanitary or unsafe conditions that are not being addressed properly
• SALVAGE BUILDING CONTENTS
• SEWAGE & SEPTIC CONTAMINANTS
• SEPTIC / SEWAGE SOIL CONTAMINATION HAZARDS
• SEPTIC TANK / FIELD INSTALLATION HEALTH HAZARDS
• SEWAGE BACKUP, WHAT TO DO
• SEWAGE CONTAMINATION in BUILDINGS
• SEWAGE CONTAMINANTS in FRUIT / VEGETABLES
• SEWAGE NITROGEN CONTAMINANTS
• SEWAGE PATHOGENS in SEPTIC SLUDGE
• Step 6. FLOOD DAMAGED BUILDING CLEAN-UP if you need general guidance following a flood
• SWIMMING WATER TESTS

Suggested citation for this web page

SEWAGE CONTAMINATION in BUILDINGS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to DRAIN SEPTIC SEWER PIPES

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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