As with any part of your home, your septic system will eventually decline over time. While age is one of the biggest reasons why septic tanks deteriorate, there are a number of other ways that your system could malfunction or become damaged. The most common reasons why septic systems fail include: Improper installation Poor maintenance routines Soil compaction or tree root invasions Weight, such as cars, on the drain field Corrosion or other environmental factors Solid items flowing down the drain Natural disasters such as flooding