Your septic system installation was a costly investment. With most new systems costing between $5,000 and $10,000, protecting that investment is crucial. Poor septic system maintenance, overloading your system, and parking cars on your drainfield are just a few things that can cause drainfield failure. But an issue that you may not consider frequently is tree roots. As the trees on your property age and grow, their root systems become extremely complex and can even interfere with your drainfield if the tree is planted to close to your drainfield.