How They Work

A septic tank is a water-tight container usually made of concrete and buried in the front or back yard of a home. It holds household wastewater long enough to allow solids to settle down to the bottom, forming sludge, while oil and grease floats to the top as scum.

Septic Tank Partially treated liquid wastewater exits the tank into a drain field, which discharges down into the soil to help remove harmful coliform bacteria, viruses and nutrients. In certain cases, this discharge can reach natural water sources.

Typical septic tanks will last about 40 years or more with regular maintenance. Most septic system failures are caused by poor maintenance.

Septic tanks can deteriorate or have other structural problems. Associated drainfields commonly clog over time, costing thousands to repair.

Concerns about Septic Tanks

Failure: Common causes of septic system failure include aging infrastructure, inappropriate design, overloading with too much wastewater in too short a period of time and poor maintenance. Septic drainfields often become clogged over years without proper maintenance. This limits the ability of partially treated sewage to seep into the soil. Septic systems then back up, flooding residential yards or home interiors.

Cost: Regular maintenance is recommended every three years at a typical cost of $250 to $500. Many owners forego the maintenance until septic tanks fail, damaging personal property. Failing septic systems can lower the value of a home, impact a pending sale or pose a legal liability with neighbors. Septic tank repairs typically cost $3,000 to $7,000.

Health Safety: Household wastewater contains disease-causing bacteria, viruses and high levels of nitrogen and phosphorus. Properly working septic systems can remove most of these pollutants. But insufficiently treated sewage from failing septic systems can drain down into the soil and contaminate natural groundwater, which can spread disease in humans and animals. Contamination also can impact other natural water bodies.