Photograph of sewer line break in a crawl space First Priority Actions for a Sewage Backup
4 Key Steps to Septic Backup or Sewer Backup Cleanup & Repair

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Sewage backup:

What to do in response to a septic or sewer backup into a building or in response to building flooding: this article explains how to respond to septic system or sewer backups in a building. Yes a toilet backing up is disgusting. It's also unsanitary and can be a serious health hazard in a building.

Here we explain the inspection, cleanup and other steps necessary to sanitize a building that has suffered flooding or sewage-contaminated backups as well as steps to return the building drain, waste, vent system to operation. This article also explains how to stop a toilet from overflowing and it offers some first aid for toilet backups and other plumbing drain or sewer piping backup conditions.

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What to do When the Septic or Sewer System Backs Up Into or Enters a Building

PHOTO of sewage contamination sludge on the floor in a basement from a sewer line backupIn this article series we explain the causes of & response to 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.

[Click any image for an enlarged, detailed version]

Just below in this article we give the first-response priorities & steps in a sewage spill or leak response.

Watch out: sewage spills contain contaminants that can cause serious illness or disease. Disease causing agents in raw sewage include bacteria, fungi, parasites, and viruses and can cause serious illnesses including Hepatitis A.

Step 1: Is the sewage-spill contaminated building safe to enter?

If a building has been flooded by sewage or wastewater there may be unsafe electrical wiring, bacterial and pathogen hazards, mold hazards, even unsafe mechanical systems.

  • Turn off electrical power in the area that has been flooded if there is any chance of electrical wires, extension cords, or electrical appliances or fixtures coming in contact with standing water or wet materials
  • Vacate sewage-contaminated areas right away. Areas of sewage spill should not be occupied by people who are not wearing appropriate protective equipment as they are dangerous:

Watch out: sewage spills contain contaminants that can cause serious illness or disease. 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.

You should assume that any surface or material touched by sewage is contaminated.

Watch out: Unless you are wearing appropriate safety gear, do not enter confined spaces that have been contaminated with sewage, as toxic, flammable or asphyxiating or even explosive gases including methane and hydrogen sulfide as well as airborne pathogens may be present.

Keep children & pets out of the sewage-spill area

At BUILDING ENTRY for DAMAGE ASSESSMENT we discuss safety procedures for people considering entering a building following a disaster including flooding or possibly sewage backups.

For sewage backups in tight spaces such as crawl areas, see CRAWL SPACE SAFETY ADVICE. Presuming that the building is safe to enter, go to step 2.

Step 2: damage control for sewage backups & spills

Toilet backupIf there are measures that can be taken to stop continued sewage entry or water spread through the building, such as stopping a TOILET OVERFLOW or even opening a door or window for fresh air or to reduce wastewater spread, do that.

  • Stop flushing toilets
  • Turn off running water that is sending water into the drain system (clothes washer, sinks etc)

If the sewage or wastewater are being spread by water from a burst plumbing supply or hot water heating pipe, turn off the water to the building and if needed for safety or to stop further you may also need to turn off the (hot water or steam) heating system.

Items that have been soaked and are not salvageable may best be placed outdoors. By removing wet and contaminated materials from the building it may be easier to inspect, repair leaks, and clean the building itself.

Watch out: do not handle sewage-contaminated materials without proper personal safety protection: there are bacterial, pathogenic, respiratory and infection hazards.

  • Remove sewage-contaminated contents: carpeting, upholstered furniture, curtains, wet books and similar items should be discarded.

    It may be possible to salvage valuable area carpets by professional cleaning and disinfection. Be sure to inform the carpet cleaning service that the area carpet was sewage-flooded. But wall to wall carpets and carpet padding that have been contaminated with sewage should be discarded.

  • Protect nearby dry, un-contaminated building contents from sewage contamination by moving them to clean dry areas outside the threat-area.

Watch out: generally we do not move already-contaminated building contents into a clean building area - doing so will simply expand the necessary scope and cost of building cleaning and disinfection. But where temporarily moving items outdoors is not practical, it may make sense to move wet or contaminated items that are to be salvaged into a concrete or tiled floor garage or similar area.

Items there can be later removed for cleaning and the clean-up of a hard-surfaced floor will be less troublesome than other surfaces.

If necessary get help from your local emergency authorities such as fire department and health department both for emergency response (such as pumping a flooded basement) or further building safety assessment.

See FLOOD DAMAGE REPAIR PRIORITIES. If the building water supply is by private well that was covered by floodwaters, also

  • Open windows or doors, open curtains, lift blinds; if weather permits, opening windows and screened doors can help reduce indoor humidity. And sunlight as well as speeding the dry-out of materials can slow bacterial growth and mold formation.

    Watch out: do not run central air conditioning or warm air heating systems in flooded areas if mold is visible or suspected or if sewage-contaminated dust and water droplets can enter the system. Doing so will contaminate the HVAC system and thus increase the cost to clean and disinfect the building. Seal off supply and return air registers in the affected area (masking tape and plastic are fine) to prevent contaminants from entering the duct system.

    If you run portable air conditioners or window units those devices may also become contaminated and may need to be replaced.
  • Call a septic tank service company if your septic system appears to have backed up into the building.

    Watch out: while pumping a septic tank can give temporary emergency relief and permit use of toilets if the sewage backup was caused by a septic tank or drainfield failure, this step is not a long-term repair. More accurate diagnosis of the cause of septic tank or drainfield failure and thus a plan for proper repairs is necessary.

Step 3: sewage backup or spill cleanup

  • Act promptly.

    Watch out: The longer that sewage waters remain in a building or on its contents the greater the chance of spreading illness or disease and the greater the chance of causing a costly mold contamination problem in addition to the sewage problem. High indoor moisture caused by standing water can cause mold contamination to form on other building surfaces even if they were not directly wet by the sewage spill.

    Don't panic: while prompt action is needed as we just explained, don't be in such a rush that you do something dangerous. Also, if you sound terrified when calling a contractor for assistance the result may be the imposition of inappropriate or costly steps.
  • Call a professional water damage restoration authority - For other than a trivial spill on a tiled bathroom floor you may need help from a professional water damage or restoration company. At the sewage cleanup procedural details article cited just below we give further help in deciding if you need to call a professional.
  • Notify your insurance company that there has been a sewage spill in the building
  • Notify your municipal authority or sewer department if your home is connected to a public sewer
  • Contact your local health department for advice if your home is connected to a private septic system
  • Sewage cleanup procedure details: including do-it-yourself advice are
    at SEWAGE CLEANUP STANDARDS we describe in more detail the steps in removing sewage & disinfecting & cleaning a building interior after a sewage backup or spill, and for a better understanding of what a competent professional will do to clean up sewage spill contamination in a building we list articles [PDF format] that give detailed standards and procedures for sewage cleanup in or even outside of buildings.
  • Crawlspaces & basements:
    at CRAWL SPACE SEWAGE CLEANUP we describe procedures for cleaning up a sewage spill inside or around buildings (not just for crawl spaces).
  • Flooded buildings: for extensive building flooding,
    at FLOOD DAMAGE CLEANUP & REPAIR GUIDE we list the steps needed for repairing a flooded home.
  • Sewage contamination testing:
    at SEWAGE BACKUP TEST & CLEANUP 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. Also see SEWAGE & SEPTIC CONTAMINANTS

Step 4: prevent a sewage backup recurrence

Inaccessible and contaminated crawl area requires special protection and debris removal before a sewage spill can be addressed (C) Daniel FriedmanDisturbing as it may sound, we find that some buildings suffer chronic flooding, leaks, sewage backups and spills. It makes sense to do more than just clean-up a sewage spill: one needs to identify and repair the underlying problem that caused the sewage overflow, spill or backup.

  • Call a professional / licensed plumber if you need help with drain de-clogging or broken drain repair

    Watch out: for homes using older ABS plastic drain piping, as we discuss
    at ABS PLASTIC PIPE, field investigations of leak stains (as in our photo) as well as investigations of sewer gas
    odors (SEWER GAS ODORS) have traced these problems to failure to properly clean, prime, and glue the pipe joints during construction.

  • Maintain the septic system: Watch out: for homes connected to a private septic system, proper septic tank maintenance, particularly pumping the septic tank on schedule is a key step in preventing septic system failure & backups.

Diagnose the cause of the sewage backup

The root cause of a sewage backup may be a simple single-event toilet overflow, a chronic
drain clog (CLOGGED DRAIN DIAGNOSIS & REPAIR) or private
septic system
failure problem (SEPTIC DRAINFIELD FAILURE DIAGNOSIS), or even a natural disaster or area flooding.

If your building has had a septic or sewage system backup into the structure you will want to review this article
and DRAIN & SEWER PIPING - where we discuss sewer line leaks.

at SEWAGE BACKUP TEST & CLEANUP 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.

If the event that caused the sewage or septic backup into the building has also left the building drain system clogged (likely if the entire system was flooded),
see BLOCKED DRAIN REPAIR METHODS to try clearing your blocked drain before going to more drastic measures. If you have had sewage back up and spill out of toilets into the building, cleanup is needed and you may face bacterial hazards.

The inspection for an underlying cause of chronic drain backups, toilet overflows, and sewage spills may need to include these less-direct causes:

Emergency Toilet Overflow Rescue Procedure - how to stop a toilet from overflowing

This topic has been moved to a separate article: please


Continue reading at SEWAGE CLEANUP STANDARDS - where we describe in more detail the steps in removing sewage & disinfecting & cleaning a building interior after a sewage backup or spill and where we provide documents with still more detail from experts on sewage spill remediation.

Suggested citation for this web page

SEWAGE BACKUP, WHAT TO DO at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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