Preventing and Solving Sewage Treatment Problems During a Flood - EH: Minnesota Department of Health

Preventing and Solving Sewage Treatment Problems During a Flood

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Preventing and Solving Sewage Treatment Problems During a Flood
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Sewage Problems During a Flood

Flood conditions can cause a number of potential problems for users of private sewage treatment (septic) systems. This web page describes steps you can take to prevent - or resolve - flood related sewage problems.

How can I prevent sewage back-up?

Flood water can increase pressure on your sewage system, leading to possible sewage back-ups. The following precautions will help prevent a sewage back-up in your home.

Sinks, bathtubs, & showers

  • Flush toilets only when necessary.
  • Take sponge baths instead of tub baths and showers.
  • Use towelettes to clean your hands - unless they are very dirty, or you are preparing food.

In the kitchen

  • Use disposable plates, cups, and silverware whenever possible.
  • Do not use your dishwasher - wash all dishes by hand.
  • Prepare food that won't get as many dishes dirty - such as canned or frozen fruits or vegetables.
  • Do not run water in the sink to get it cool - use ice or cool it in the refrigerator, instead.

In the laundry

  • Take your laundry to the Laundromat - don't do it at home.

And, in general

  • Avoid discharging water into floor drains.
  • If you use a sump pump, do not pump the effluent into a septic tank.
  • Do not use your water softener.
  • Check for leaky faucets and water pipes.


  • Whenever the water table is high - or your sewage system is threatened by flood water - you run the risk that sewage will back up into your home.
  • Relieving pressure on the system - by using it less is the only way you can prevent a back-up.

What if a back-up does happen?

If you do end up with a sewage back-up problem, the following steps will help keep the damage to a minimum.

  • Begin by removing all floor drain covers.
  • Use mechanical metal grip plugs to seal the drains - and prevent sewage from entering the home.
  • Repeat the process for toilets, bathtub drains, and shower drains.
  • Metal grip plugs are available at plumbing supply stores.

What if my system become flooded?

Stop using your sewage system

  • If your septic tank or drainfield becomes flooded.
  • If you can see any raw sewage or "grey water" on the surface of the ground, as a result of waste water leaking from your system.
  • If wastewater begins to enter your home through drains or plumbing fixtures.

After the flood

If your drainfield has been flooded, you may or may not be able to use it again. You may need to relocate your drainfield to a site with more suitable soil conditions.

If you need help in determining whether to relocate your drainfield, contact your local planning or zoning office.

What do I need to do after the flood is over?

After the flood waters recede, check to see if any major system components have been under water.

Check septic tanks, drop boxes, distribution boxes, lift stations, and any other vault type structures. If any portion of the system has been in contact with flood water, be sure to pump out all solids and liquids before using the system again.

If your drainfield was under water, you will need to wait until the soil dries out sufficiently before using the system. There should be no saturated soil within three feet of the system, and there should be at least three feet of unsaturated soil between the bottom of the system and the water table.

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Updated Wednesday, April 01, 2015 at 10:45AM