If properly maintained, most systems last anywhere from 20 to 40 years. The most common reason for early failure is improper maintenance. When a system is not pumped out on a regular basis, solids build up in the septic tank and can flow into the leach field. This can cause the system to fail. Abusing a system will also cause it to fail. Abusing a system is using more water than the system is designed for or dumping fat and grease down the drains.