How a Septic System Fails

A septic system can fail by two methods: a mechanical failure of a component or biologically. The systems installed in the past 30 years are made from durable materials. Prior to then, some components were marginally durable by today’s standards. Many times these failed components can be upgraded to more modern materials.

Mechanical Failures

Most septic tank designs are very durable and seldom need replacement. The typical failure mode of a tank is caused by corrosion. Plastic and fiberglass tanks are not susceptible to corrosion unlike concrete and steel. The concrete tanks can deteriorate from exposure to the hydrogen sulfide gas (rotten egg odor) produced by the anaerobic bio-chemical process. Steel tanks can rust from two sources, the hydrogen sulfide gas and general oxidation. If the tank is manufactured using industry standard materials a mechanical failure is not likely.

Mechanical failures are generally caused by human error such as crushing or collapsing the tank with heavy equipment or improper installation. The pipe system to and from the tank is also very durable. While durable, cast iron pipes can be problematic because of corrosion. The inlet and outlet pipes can be damaged through crushing with heavy equipment. The pipes can also fracture if the soil below and adjacent to the tank was not properly compacted during installation; however, this is the exception.

Biological Failures

More likely, a septic system is going to fail biologically. As described in How a Septic System Works the maturing of the biomat is the number one cause of septic system failure. By design, the biomat will grow at the infiltrative surface of the dispersal module. Theoretically, the natural aerobic soil bacteria will keep the biomat permeable enough for the system to function. This theory is correct for a finite period of time. On average the biomat will mature into a non-permeable layer in about 15 - 20 years of service.

When the biomat is no longer permeable the dispersal module is considered failed and the problem needs to be addressed. The range of service life is wide, anywhere from 5 years to 60 years. The service life is definitely influence by many factors such as soil types, climate, installation techniques, abuse, and proper maintenance.

What To Do When Failure Occurs

When septic system failure occurs, the conventional solution is to replace the dispersal module through excavation. While this solution is effective for a finite time period, the replacement module will fail again within 5 - 60 years. The science based solution to restoring dispersal modules is conversion of the bio-chemical process to an aerobic environment by installing the On-Site Treatment Systems Aerobic Recovery Unit™!