PVC pipe is often used for underground drainage. The pipes carry water away from home foundations through a French drain and deposit it into a safe place, either farther away from the home or close enough to a sewer drain where it can run off. PVC pipes are also used in septic fields to carry waste to the field. The pipes are virtually indestructible but can clog with debris and plant roots.
Roots and Water
PVC drainage pipes are perforated along the length to allow water from the area to drain off. Almost all plants are good at finding water, but some in particular have an affinity for sending roots into the smallest crevice to seek out moisture. If they find their way into a PVC drainage pipe, they will easily clog it up with root mass. Planting flowers, trees or bushes too close to a PVC drainage pipe will cause future problems.
Trees such as willows, red and silver maples, beeches, birches, elms and poplars are heavy water feeders and will find a way into the PVC pipes unless they are at least two to three times their height away from the pipes. Other plants to avoid close to the pipes are woody shrubs and annuals -- plants that do not die back at winter. Keep them at least 10 feet from any underground drainage system.
Safe to Plant
Shallow-rooted ornamental grasses can cover PVC pipes without a problem. Bulbs such as lilies, hyacinths, daffodils and tulips also work fine over PVC pipes. Other popular perrinniels such as columbine, begonias, forget-me-nots and violets are safe to plant near a buried PVC pipe.
Chemical control can ease the problem of excessive root growth in PVC pipes used for sewage, but do not use them around pipes used for foundational drainage. Removal of the roots with copper sulfate, dichlobenil or metam sodium will free up the line without doing any damage to the tree or shrub. These chemicals are dangerous and should only be used as government regulations prescribe.
If you sell the home, the future owner may need to know where the pipe is. Once PVC goes into the ground it is impossible to detect without digging unless it is marked. Before laying the pipe it is a good idea to glue a strip of copper, such as plastic-coated lamp cord, along the upper top and length of the pipe. If someone needs to find the pipe again, or if the utility company is checking for buried pipes it will easily show up on their instruments.