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Septic Systems - What to Do after a Flood - Septic Flood Response, Safety, Health, Maintenance, Repair Advice
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Critical Post-Flood Septic System Advice

The following text is not part of the original US EPA document but has been added by this website author.

Immediate Serious Safety Hazards: Property owners whose septic system has been flooded should be concerned first for immediate safety hazards such as the increased risk of a dangerous collapse of a site-built septic tank, drywell, or cesspool. A site-built system, such as a cesspool made of dry-laid stone or concrete blocks, may have been weakened by floodwaters. Rope off and prevent access to the area where such systems are installed until you have made certain that there is no danger of collapse. Someone walking over a weakened septic tank cover or cesspool or drywell could fall in - a possible fatal event. Never leave the cover off of a septic tank, cesspool, or manhole. Someone can fall-in.

Electrical Hazards: if your septic system includes electrical components such as pumps, be sure that electrical power has been turned off before attempting to examine the equipment.

Health Hazards: the EPA advice on this topic (below) refers to the high risk of sewage backup into homes during flooding. Sewage backup into a home leaves a variety of pathogens and creates a serious risk of hidden mold in buildings. Both of these can create health hazards, particularly for people who are at extra risk: infants, the elderly, people who are immune-impaired, people with asthma, etc. Further investigation, testing, and cleaning are likely to be in order. A simple "pumpout" of a flooded basement, for example, may leave wet building materials and insulation if the basement walls were finished with drywall or paneling. In these cases the wet materials should be removed promptly, the area dried, cleaned if needed, and inspected for evidence of contamination before rebuilding.

Major Structural or System Damage: do not enter a flooded structure if there is evidence that the building may be unstable or in danger of collapse. A building which has shifted off of its foundations, evidence of subsidence (depressions in the soil) over or near a septic system (or anywhere else), or buckled foundation walls are examples of dangerous conditions that merit professional inspection and advice.

Manholes and Tank Covers may have shifted or may even have been lost during flooding. Falling into an open septic tank or sewer is likely to be fatal. Watch for open, shifted, damaged, or otherwise unsafe covers or openings to these systems.

Property owners whose septic systems have been flooded should read the following articles as well as the advice offered from the U.S. Environmental Protection Agency and re-printed below.

• Cesspool Safety Warnings include dangers of cave-in and fatality
• Contamination in Buildings how to test buildings for bacterial contamination from Sewage and Septic backup, remediation, & references
• Septic System Safety: Septic System, Septic Tank, & Cesspool Safety Warnings for Septic Inspectors, Septic Pumpers, and Homeowners

The information below is provided by the U.S. EPA. Additional comments or suggestions, where provided by the web author, will be flagged as added text (such as the paragraphs preceding this section. I have re-ordered some of the original EPA text to put the obvious and most important information first. [DJF]

What do I do with my septic system after the flood?

Once floodwaters have receded, there are several things homeowners should remember:

• Do not drink well water until it is tested. Contact your local health department.
• Do not use the sewage system until the water level in the soil absorption field is lower than the water level around the house.
• Have your septic tank professionally inspected and serviced if you suspect damage. Signs of damage include settling or an inability to accept water. Most septic tanks are not damaged by flooding since they are below ground and completely covered. However, septic tanks and pump chambers can fill with silt and debris, and must be professionally cleaned. If the soil absorption field is clogged with silt, a new system may have to be installed. [DF: check the area of the drain field for piping which has become exposed (soil loss) or piping which has become clogged with mud and silt.]
• Only trained specialists should clean or repair septic tanks because tanks may contain dangerous gases. Contact your health department for a list of septic system contractors who work in your area.
• If sewage has backed up into the basement, clean the area and disinfect the floor. Use a chlorine solution of a half cup of chlorine bleach to each gallon of water to disinfect the area thoroughly.
• Pump the septic system as soon as possible after the flood. Be sure to pump both the tank and lift station. This will remove silt and debris that may have washed into the system. Do not pump the tank during flooded or saturated drainfield conditions. At best, pumping the tank is only a temporary solution. Under worst conditions, pumping it out could cause the tank to try to float out of the ground and may damage the inlet and outlet pipes.
• Do not compact the soil over the soil absorption field by driving or operating equipment in the area. Saturated soil is especially susceptible to compaction, which can reduce the soil absorption field's ability to treat wastewater and lead to system failure.
• Examine all electrical connections for damage before restoring electricity.
• Be sure the septic tank's manhole cover is secure and that inspection ports have not been blocked or damaged.
• Check the vegetation over your septic tank and soil absorption field. Repair erosion damage and sod or reseed areas as necessary to provide turf grass cover.
• [DF: if your septic system uses special equipment such as a packaged aerobic treatment unit or other packaged wastewater treatment systems, check with the system manufacturer. Some manufacturers will void the system warranty if sealed components are opened by the homeowner.]

Remember: Whenever the water table is high or your sewage system is threatened by flooding there is a risk that sewage will back up into your home. The only way to prevent this backup is to relieve pressure on the system by using it less.

Where can I find information on my septic system?

Please contact your local health department for additional advice and assistance.

For more information on onsite/decentralized wastewater systems, call the National Environmental Services Center at (800) 624-8301 or visit their website at www.nesc.wvu.edu.Exit EPA Disclaimer

How to Find The Septic Tank - (added by web author)

• Septic Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location

Do I pump my tank during flooded or saturated drainfield conditions?

No! At best, pumping the tank is only a temporary solution. Under worst conditions, pumping it out could cause the tank to try to float out of the ground and may damage the inlet and outlet pipes. The best solution is to plug all drains in the basement and drastically reduce water use in the house.

[DF NOTE: As the EPA says above, however, pump and inspect the septic system (including the piping) as soon as possible after the flood, just not so soon that there is risk of floating the septic tank. If a septic system is not going to be used for months and wet weather or high ground water conditions are expected to continue, I would not pump a fiberglass or plastic septic tank as there is risk that the tank will float up out of the ground. This is not much of a risk with concrete septic tanks. Be sure to pump both the tank and lift station. Further inspection for safety as well as the overall condition of the system is needed.]

When to Pump a Septic Tank - (added by web author)

• Septic Tank Pumping Frequency Guide for Septic Tanks: When, How, What to Watch For when pumping or cleaning septic tanks

What if my septic system has been used to dispose wastewater from my business (either a home-based or small business)?

In addition to raw sewage, small businesses may use their septic system to dispose of wastewater containing chemicals. If your septic system that receives chemicals backs up into a basement or drain field take extra precautions to prevent skin, eye and inhalation contact. The proper clean-up depends of what chemicals are found in the wastewater. Contact your State or EPA for specific clean-up information.

What are some suggestions offered by experts for homeowners with flooded septic systems?

• Use common sense. If possible, don't use the system if the soil is saturated and flooded. The wastewater will not be treated and will become a source of pollution. Conserve water as much as possible while the system restores itself and the water table fails.
• Prevent silt from entering septic systems that have pump chambers. When the pump chambers are flooded, silt has a tendency to settle in the chambers and will clog the drainfield if it is not removed.
• Do not open the septic tank for pumping while the soil is still saturated. Mud and silt may enter the tank and end up in the drainfield. Furthermore, pumping out a tank that is in saturated soil may cause it to "pop out" of the ground. (Likewise, recently installed systems may "pop out" of the ground more readily than older systems because the soil has not had enough time to settle and compact.)
• Do not dig into the tank or drainfield area while the soil is still wet or flooded. Try to avoid any work on or around the disposal field with heavy machinery while the soil is still wet. These activities will ruin the soil conductivity.
• Flooding of the septic tank will have lifted the floating crust of fats and grease in the septic tank. Some of this scum may have floated and/or partially plugged the outlet tee. If the septic system backs up into the house check the tank first for outlet blockage. Clean up any floodwater in the house without dumping it into the sink or toilet and allow enough time for the water to recede. Floodwaters from the house that are passed through or pumped through the septic tank will cause higher flows through the system. This may cause solids to transfer from the septic tank to the drainfield and will cause clogging.
• Locate any electrical or mechanical devices the system may have that could be flooded to avoid contact with them until they are dry and clean.
• Aerobic plants, upflow filters, trickling filters, and other media filters have a tendency to clog due to mud and sediment. These systems will need to be washed and raked.

End of US EPA text

More Reading About Septic System Inspection & Repair After Building or Septic Sytsem Backups or Flooding - (added by web author)

• The Septic System Information Website Home Page: public information website about septic system design, installation, maintenance, and repair
• Cesspools Home Buyer's or Owner's Advice
• Cesspool Safety Warnings include dangers of cave-in and fatality
• Drywells Home Buyer's or Owner's Advice
• Mold Action Guide after Flooding: How to Minimize Mold Damage After a Building Flood
• Septic System Safety: Septic System, Septic Tank, & Cesspool Safety Warnings for Septic Inspectors, Septic Pumpers, and Homeowners
• Sewage & Septic Backups and what to do about sewage spillage in buildings
• Sewage Contaminants which may be released from sewage spills from residential septic systems and wastewater disposal systems
• Sewer Gas Odors diagnosing, finding, and curing septic tank and sewer line smells
• Sewer Gas - Methane and other septic system gas explosion or asphyxiation hazards such as hydrogen sulfide
• Septic Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
• Tank Location - How to Find the Septic Tank, how deep will the cover be, how to document its location
• Tank Pumping Frequency Guide for Septic Tanks: When, How, What to Watch For when pumping or cleaning septic tanks
• Ten Steps to Keeping a Septic System Working, suggestions from the U.S. EPA, edits and additions by DJF
• What is a Septic System An Engineer's View & Septic System FAQ's

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.

• Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06
• Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com 11/06
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. 11/29/06
• Daniel Friedman - principal author
• Technical reviewers are invited to comment or ask questions - contact us

More expert information on this topic

More Information on Septic System Diagnosis, Maintenance, & Repair

• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Home & Outdoor Living Water Requirements
• Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
• How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
• Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
• Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.


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.)

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