First, tree roots invade mostly through lines that are damaged and in the top 24 inches of soil. Sound lines and sewers have very little trouble with root damage and only at weak points where water is seeping out. The larger, fast growing trees are the biggest problem. Avoid planting these trees near your service and watch very carefully these kinds of trees near your service.
Roots don't actually crush septic tanks and lines, but rather enter at weak and seeping spots on tanks and lines. Many fast-growing, large trees are considered more aggressive toward water service when finding a water source coming from that service. Try to avoid planting these large, fast-growing, aggressive-rooted trees to include 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).