What To Do With Your Septic System During A Flood

This fact sheet is provided to assist property owners served by subsurface sewage treatment systems (SSTS or septic systems) on what to do before, during and after a flood.
What can I do if I am in a flood prone area well in advance of a flood?
• Have a licensed plumber install a backflow preventer on the building sewer so sewage cannot backup into your home during a flood. A backflow preventer is recommended if there is some concern a simple check value may not close properly and sewage may back-up into the home.
• Make sure all inspection caps are in place. Threaded caps can be installed and the pipes can be cut flush with the ground.
Immediately Prior
What can I do immediately prior to a flooding event?
• If the building sewer has a backflow preventer, nothing further needs to be done.
• If the backflow preventer is a manual valve, ensure it is shut.
• If the tank does not have a backflow preventer, it may be desirable to pump the tank to remove the sewage, but the tank must be properly anchored. Tank pumping immediately prior to flooding is not mandatory. If pumped, some sewage solids will remain in the tank and could mix with any floodwaters that enter the tank. It may be advantageous to block any lower level drains in the dwelling to prevent back-up.
• Make plans to minimize water use or flushing of toilets during the actual flooding event.
What should I do during the flood if the system is covered with water?
• Do not use the system. Turn off water softeners to prevent them from regeneration. Turn off all the system’s electric devices (pumps, alarms, etc.)
• If you are using water from a flooded well, it may be contaminated. Contact a well professional or your county about a water test.
Once the floodwaters recede, when can I use my system again?
Do not use the system until:
• The soil has adequately dried to allow sewage to be absorbed and not back-up. This may take several weeks. You should try to conserve water until the system is completely dry.
• All tanks have been checked to see if they contain floodwaters. If so, the tanks should be pumped to keep the silt particles from entering the soil system. If the tanks have not been anchored, do not pump until the water level in the soil is below the tank.
• Effluent screens (if any) are cleaned.
• The electrical system (if any) has been inspected. This includes electrical connections, pumps, alarms, etc.
• If your system has an advanced treatment device you should check with your licensed service provider before operation.
• All tank maintenance hole openings must be immediately secured, repaired, or replaced if the covers have been shifted, moved or lost in the flood.
• Any obvious damage has been repaired.
How do I know if my system is damaged?
Signs of damage include:
• Settling of soil over the tank or soil system.
• Inability of the system to accept wastewater, indicated by sewage back-up or surfacing on the ground.
If you observe either of the above after floodwaters recede, contact a SSTS professional. They can be found through local advertizing or at: http://www.pca.state.mn.us/index.php/water/water-types-and-programs/wastewater/subsurface-sewage-treatment-system-ssts/ssts-search.html
. What concerns are there with home clean-up activities and my septic system?
• The home cleaning process will likely result in the discharge of high amounts of disinfectants and cleaners into the septic tank. It is best to pump the tanks (a second time if floodwaters were previously pumped) to avoid discharging of these chemicals into the soil portion of the septic system.
• Do not dump floodwaters that have entered the house into a plumbing fixture which discharges into the SSTS.
• Do not drive vehicles and equipment over the system during clean-up or restoration activities. Do not set dumpsters or building materials over the system. Fence-off the system to protect it.
What should I do with my septic system soon after the flood?
• Inspect the vegetation over your septic tank and soil absorption field.
○ Repair erosion damage and sod or reseed areas as necessary to provide proper cover.
What septic system work can I do myself?
• Due to the many hazards in working with septic systems (disease transmission, poisonous gasses, and electrical shock) it is strongly recommended that all septic system work be conducted by a SSTS licensed business or licensed electrician for electrical work.
○ If these professionals have determined there is no damage to your system, a homeowner may re-sod or re-seed a damaged area.
Where can I find information about maintaining my septic system?
• Contact your county Environmental Services or Planning and Zoning Department for additional advice and assistance.
• A septic system owner’s guide is available from the University of Minnesota at: http://www.extension.umn.edu/distribution/naturalresources/DD6583.html with more flooding information at: http://septic.umn.edu/factsheets/flooddamageprotection/index.htm.
You may also call the Minnesota Pollution Control Agency at 800-657-3864 with any SSTS flood related questions.
Source: Minnesota Pollution Control Agency

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