Tree Roots in Sewer and Water Lines

Dealing With Tree Roots in Ground Utility Lines and Pipes

Sycamore Root Near House Foundation
Steve Nix

Conventional wisdom lends that certain tree species may be more harmful than others to water and sewage lines especially if planted too close to these utilities. That wisdom weighs out as far as it goes, but all trees have some ability to invade water and sewer lines.

Tree roots invade mostly through damaged lines installed in the top 24 inches of soil. Sound lines and sewers have very little trouble with root damage, and then only at weak points where water seeps out.

Aggression toward water service in many fast-growing, large trees is spawned by the discovery of a water source coming from that service -- as is the case with any living thing, a tree will do what it must to survive. Roots don't actually crush septic tanks and lines; instead, entering through weak and seeping spots on tanks and lines.

Avoid planting aggressive growers such as Fraxinus (ash), Liquidambar (sweetgum), Populus (poplar and cottonwood), Quercus (oak, usually lowland varieties), Robinia (locust), Salix (willow), Tilia (basswood), Liriodendron (tuliptree) and Platanus (sycamore), as well as many Acer species (red, sugar, Norway and silver maples and boxelder) near your water service and watch these kinds of trees very closely near your sewage service.

Managing Trees Around Sewers and Pipes

For managed landscapes near sewer lines, replace water-seeking trees every eight to 10 years before they grow too big. This limits the distance roots grow outside the planting area and the time they have to grow into and around sewer lines as well as foundations, sidewalks, and other infrastructure.

Older trees can embed pipes and sewers by growing roots around the pipes. If these trees experience a structural root failure and topple, these field lines can be destroyed, so it is important to keep a close eye on these as well.

The University of Tennessee recommends these steps to help prevent tree root damage:

  • Plant small, slow-growing trees near sewer lines.
  • If faster-growing species are desired, plan to replace trees every eight to 10 years.
  • Even slow-growing trees will eventually interfere with sewer lines, so these trees must be monitored and replaced periodically.
  • When building new sewer lines or improving existing lines, consider landscaping plans and potential root intrusion from trees.

UT further recommends these common trees as planting options near water and sewer lines: Amur maple, Japanese maple, dogwood, redbud, and fringetree.

Options exist if you already have tree root damage to your lines. Products containing slow-release chemicals to stymie further root growth are helpful. Other root barriers include densely-compacted layers of soil; chemical layers such as sulfur, sodium, zinc, borate, salt or herbicides; air gaps using large stones; solid barriers such as plastic, metal, or wood.

Each of these barriers can be effective in the short term, but long-term results are difficult to guarantee and can significantly harm the tree. Seek professional advice when using these options.