Flooded Septic Systems - What to Do after a Flood

  • FLOODED SEPTIC SYSTEMS, REPAIR - CONTENTS: How to evaluate & repair or return to service a flooded septic tank & septic fields. Safety advice for flooded septic systems & how to get a flooded septic system working again, when to pump the septic tank, what to look for. Flood damage septic systems. Septic system flooding research.
  • POST a QUESTION or READ FAQs about flooded septic tanks and flooded drainfields or soakaway beds - what to do to restore the septic system to safe functional operation
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Flooded septic tanks and drainfields - advice:

If your septic system has been exposed to flooding, this document gives immediate safety and health advice and includes other advice from the U.S. EPA and other septic system experts. We set priorities: safety, health, maintenance, and repair for septic systems after flooding.

Yin et als (2011) point out that problems associated with flooded septic systems will increase significantly as sea levels and tide levels continue to rise around the world. In addition to describing steps to return a septic system to operation after flooding, this article includes recommendations and research on the construction of flood-damage-resistant decentralized or onsite septic systems.

The photo at page top shows storm-flooding of Wappingers Creek in Dutchess County, New York. Homes built along this creek have septic soakbeds or drainfields located not only in a flood zone but too close to this waterway. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted

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Returning a Flooded Septic System to Service: Critical Post-Flood Septic System Advice

Article Series Contents

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

Emergency Response: Septic System Safety in Flooded Areas

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.

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:

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 EPA Disclaimer

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

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)

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.

Suggestions for Homeowners with Flooded Septic Systems?

End of edited, supplemented US EPA text

Suggestions for Designing a Flood-zone Damage Resistant Septic System 

This topic has been moved to SEPTIC DESIGN for FLOOD DAMAGE RESISTANCE

Flooded Septic System Research


Continue reading at SEPTIC DESIGN for FLOOD DAMAGE RESISTANCE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SEWAGE BACKUP, WHAT TO DO - separate article with more advice for cleaning up after a sewage backup


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FLOODED SEPTIC SYSTEMS, REPAIR at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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