Protecting Your Septic System from Flooding

Rain events that lead to local flooding happen all across Pennsylvania. If there are forecasted floods for your community or a flood has already occurred, take a moment to protect your septic system and property. Here are some things to consider before, during, and after a flood.

Too much water in your septic system's drainfield may cause it to overload and may slow down or stop the treatment of your wastewater. If this occurs, you may risk septic waste backing up into your home, particularly if your drainfield becomes clogged. In wet weather, a rain-soaked drainfield may become too saturated to operate correctly for the effluent (liquid portion of your wastewater) to percolate down through the soil. You can take steps before this happens to help protect your system.

Before a Flood

As a preventive management step, you should direct your stormwater runoff away from your system as much as possible. You should divert water from roofs and driveways away from the septic tank and drainfield area. Make sure your downspouts aren't pointed directly at your drainfield. The soil over your system should be mounded slightly to encourage stormwater to flow off it instead of onto it.

A well-maintained septic system is better able to withstand the stresses of heavy rains or flooding. Have your septic system inspected annually to look for signs that the system is clogged or not emptying properly. You should check the drainfield periodically for odors, wet spots, or surfacing sewage. Have a professional check the sludge and scum levels inside the tank and inspect the baffles to ensure they are present and not severely corroded.

Schedule a professional to pump your septic tank on a routine basis. Pumping is an essential ongoing maintenance step. Your municipality might even require it on a two or three-year schedule. However, if a flood is imminent or has happened, delay your pumping until water levels have receded to normal. An empty septic tank can be buoyant and rise out of the ground during a flood.

When a septic tank overfills with floodwaters, the water will look for any path to escape, which could be up through your showers, sinks, and toilets. If you live in a flood-prone area, consider having a licensed plumber install a backflow preventer on the building sewer so sewage cannot back up into your home during a flood.

If you know a potential flood is coming, you should minimize water use in your home. Try to limit showers, laundry, and other activities that could put a lot of water into your system. If your tank or drainfield becomes saturated or flooded during heavy rains, it could lead to long-term problems. Outcomes could include solids entering and clogging your drainfield, sediments, and soils entering your tank, and backups entering your home.

During a Flood

Do your best not to use your septic system during a flood. 

If flood waters enter your home, do not pump them into your sinks or toilets. Those drains will direct even more flood water into your septic system.

Turn off your household water treatment devices that automatically run and discharge water on a cycle (like water softener recharging) 

After a Flood

Do not use your septic system until water in your drainfield has receded below your home's level. If you suspect damage, do not use it until a professional has properly inspected it. If your tank has filled with soil and sediments, you do not want to encourage their movement out of your tank and into the perforated pipe in your drainfield. They can lead to significant clogs and further problems.

If you have a private well or spring, do not drink your water until you can get it tested for contaminants from your septic system, such as E. coli bacteria and nitrates.

You should get your tank pumped after a flood, but not until water levels have receded. An empty tank may still pop out of the ground, and opening the tank while in saturated soil can lead to sediment and soil entering the tank.

More Information

Additional information on managing your septic system during a flood is available from the U.S. EPA publication "Septic Systems - What to Do after the Flood" and the PA DEP factsheet, "What To Do With Your Septic System After A Flood." You can also contact your local municipality or Sewage Enforcement Officer for additional advice and assistance.

Engineers and scientists who answer wastewater-related questions can be reached via the National Small Flows Clearinghouse assistance lines at 304-293-4191 or 800-624-8301. Read more at the National Environmental Services Center.