Serving: King County, Snohomish County, & Pierce County

Be Careful When Planting a Tree near a Sewer Line

Something to think about as you work in your yard and plan improvements this Spring…

Trees don’t actively seek out sewer lines, but their roots are attracted to moisture in the soil. Sewer lines hold not only moisture, but oxygen and nutrients, essential elements for healthy tree growth. When trees are planted too closely, the roots can grow into the sewer line, causing backups and flooding.

All trees should be planted no closer than 10 feet from sewer lines, some even more depending on the type of tree. Some water-loving trees have shallow, aggressive tree roots that can cause major problems in sewage lines down the road. Plant fast-growing, thirsty trees, such as cottonwoods and willows at least 20 to 30 feet away from sewer lines. Large trees, such as oaks and maples, grow more slowly, but eventually their roots can invade sewer lines, as well. The size of a tree’s root system is about the same as the size of the full grown tree itself, so a large oak or maple’s roots can spread extensively under the earth. To keep sewer lines free of tree roots, plant small, slow-growing trees instead.