With Hurricane Harvey in the rearview mirror and Hurricane Irma on the way, here's what to do with flooded septic systems


Days after Hurricane Harvey left southeastern Texas and Louisiana’s Gulf Coast underwater, another powerful hurricane could collide with Florida this weekend. With the prospect of another storm on the way, it’s a good time to brush up on the proper care of septic systems during flooding events.

Once heavy rains start to fall and a flood is underway, make sure to tell homeowners to cease water usage going to the system. Depending on the elevation of the septic tank and floodwaters, the tank can be used as a holding tank. The amount of damage to the system is related to the elevation of the flooding over the system combined with the length of time the system is flooded. 

When evaluating systems during flooding, make sure all inspection ports, lids and covers are properly capped and in place. Pumps and controls in the system can be removed and stored; remember to shut off electricity to the system. There should be no connections between the floor or foundation drains in the house and the system where water can drain through the system. 

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After the storm

After the floodwaters recede, the system shouldn’t be used until the soil has adequately dried to allow sewage to be absorbed without backing up, which could take several weeks. The homeowner should conserve water during that time.

A comprehensive system inspection and assessment should also be conducted before putting the system back in use. This means opening all parts of the system — sewage tanks, drop boxes, anywhere there is access to system components — and assessing whether sediment or vegetative debris has entered the system. All sewage tanks should be pumped and cleaned out.

The tanks should be evaluated for watertightness and structural defects due to the flooding. Debris in the drop boxes should be removed. If there are pumps and a pressure distribution system, the distribution laterals should be jetted and cleaned. Pumps and controls should be reinstalled, recalibrated and tested.

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The evaluation should include making sure wastewater moves between the parts of the system as intended. This may involve running a hydraulic load test on the soil treatment part of the system.

About a month after the system is restarted, the service provider should schedule a follow-up visit to check for proper operation. Any pumps and controls should be checked and the pump calibrations re-evaluated to make sure they are delivering the correct amount of effluent.

Septic tank manhole covers should be secured and inspection ports should be free of blockage and damage. Make sure there’s no damage caused by animal intrusion in the soil treatment area.

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Inspections also should include a look at the vegetation over the septic tank, and any erosion damage should be repaired with sod or seeding to provide good plant cover.

If sewage backed up inside the home, the property owner should thoroughly disinfect the house, but they should avoid flushing disinfectants down the drain.

Destroyed systems

Floodwaters can cause components of a septic system to be partially or completely washed away. The owner of such a system shouldn’t assume that soil or other fill can be added and new system components constructed.

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Heavy rains can cause slides to partially or completely cover septic system components with rock, mud or silt. These slides can affect the operational integrity of the system, especially the soil treatment systems.

When removing slide debris from the area on or around a septic system, the technician should protect the system components, taking special care to keep vehicle and equipment traffic off the soil treatment system to avoid compaction.

If the soil treatment system is saturated or has standing water long after other areas have dried out, there may be a long-term problem related to the flood.

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Sara Heger, Ph.D., and Jim Anderson, Ph.D., contributed to this article 


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