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This document provides information about sewage backup hazards, testing, inspection, and cleanup- remediation in residential and commercial buildings. 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.

The photo above shows what dirt and sewage sludge may look like in a basement after a sewer line backup. © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

Testing For Bacterial Contamination and Cleaning Up Sewage Backups in Buildings

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 at left 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 a concern, 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 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

The photograph shows a rather innocent-looking wet concrete basement floor following a sewer line backup into this builidng. 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.

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 coliform (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.

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.

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.

More Reading

• SEPTIC BACKUP PREVENTION
• SEPTIC BACKUP REPAIR
• Septic Contaminants, identifying - what are the contaminants produced by septic systems and what can be done about them if they escape initial treatment?
• Sewage and Septic Contamination in Residential Buildings - consumer information and expert resources (this web page)
• Sewage Pathogens in Septic Tank Sludge and Floating Scum: what makes up the contents of residential sewage
• The Septic Information Website - Inspecting, Designing, & Maintaining Residential Septic Systems
• Septic System Flood Response - what to do when a septic system has been exposed to flood waters

Technical Reviewers

Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.

• Daniel Friedman - principal author
• Technical reviewers are invited to comment or ask questions - contact us

More expert information on this topic

More Information on Building Diagnostic Inspections and Repairs

• Septic Contaminants, identifying - what are the contaminants produced by septic systems and what can be done about them if they escape initial treatment?
• Sewage and Septic Contamination in Residential Buildings - consumer information and expert resources (this web page)
• Sewage Pathogens in Septic Tank Sludge and Floating Scum: what makes up the contents of residential sewage
• The Septic Information Website - Inspecting, Designing, & Maintaining Residential Septic Systems
• Drinking Water Contamination and Pollution How to Detect, Test, Correct, and Prevent Well Water Contamination - US EPA - Groundwater
• Remediation of Sewage Contaminated Crawlspaces - Byjim Holland, CR, "Cleaning and Restoration," July 1999, pp 22-24
• Escherichia coli O157:H7- US CDC
• Demistifying Ecoli - Federation of Ontario Cottagers
• Microbiology home page - US EPA
• Cost effective testing for blackwater contamination in buildings Aerotech Labs
• Indicator organisms, testing for sewage contamination in buildings Aerotech Labs

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