Louisiana State Plumbing Code requires that a clean out must be installed where the main sewer line leaves the house. These clean outs often get covered up under a flower bed because it was installed at or below ground level. This clean out location accounts for 50% of main sewer problems in Baton Rouge.
One of the reasons causing main sewer problems is roots. When there are plants or trees there are roots. If a fitting is not properly glued or assembled, moisture will seep out attracting roots.
Mock Plumbing strongly recommends installing all sewer clean outs high enough not to get covered up by any landscaping. Lastly, always use a sch. 40 PVC pipe for main sewer lines.