There could be several factors affecting whether a septic system will fail including age, soil conditions, water usage and the level of maintenance. Many system drain fields fail because of tree roots that grow into the trenches seeking water and nutrients. Many other systems fail because of leaking plumbing that overloads the septic system drain field.
All septic systems will eventually reach their capacity to treat and absorb wastewater. For this reason, it is important to know where your repair area is and to make sure that nothing happens to it.