By DHEC Communications Staff
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.

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.

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

• 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.
• 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.
• 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.
• 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 falls.
• 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.)
• 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.
• 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.

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 drainfield, take extra precautions to prevent skin, eye and inhalation contact. The proper clean-up depends of what chemicals are found in the wastewater. Contact DHEC or EPA for specific clean-up information.

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

If your septic tank has overflowed, visible solids should be disinfected with lime and cleaned up.  Be sure to wash your hands throughly when finished.

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

• Boil water before drinking until you have disinfected and tested your well.  Contact DHEC.
• Do not use the sewage system until water 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.
• Only trained specialists should clean or repair septic tanks because tanks may contain dangerous gases. Contact DHEC 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.

Click here to find your local DHEC Environment office.  Additional resources may be found on the EPA’s website or CDC’s website.