Sewer Smart Planting Guide
What you need to know to
avoid causing planting-related sewer problems
Your home’s sewer is connected to the sewer “main” (a large pipe often running under the street) via a pipe known as a “lateral” that extends from your home, across your property and into the sewer main. Responsibility for maintenance of this lateral varies from community-to-community, but, in most cases the homeowner is responsible for the lateral at least out to the property line.
Regardless of who is responsible, blockages in the lateral are always bad news for the homeowner as they can lead to slow downs or complete stoppages of the flow of waste from the home and into the sewer main. When either of these situations occurs, a backup of the home’s own sewage out of the lowest opening in the home (downstairs toilet, shower, etc.) is the likely result.
Is My Lateral at Risk of Tree Root Invasion?
Depending on the age of your home, your sewer lateral may be made of either tile, cast iron, concrete or plastic. No matter the construction, your lateral is filled with water and other nutrients that make it an attractive target for tree roots.
Movement of the lateral over the years due to earthquakes and shifting soil may have created openings in it that give tree roots lucrative targets and points of entry to the pipe itself.
Once roots find a moist spot caused by sewer lines, they'll grow right into the pipe itself. And, that means you may be in for expensive plumbing repairs.
Of course, it’s best to avoid this unhappy circumstance by knowing what, where and how to plant trees with avoiding sewer problems in mind! You can help by following the sewer maintenance tips (link to tips) found elsewhere on this Website and by following some simple rules for planting above or near your sewer lateral.
Sewer Smart Planting Suggestions – Finding Your Lateral
The first step in observing Sewer Smart planting rules is to know, at least generally, where your lateral runs across your property and into the sewer main.
One of the best ways to find your lateral is to refer to the survey documents you likely received when you purchased your home. If you don’t have these documents, your city planning or public works department can likely provide copies for you to view. In some cities, they’re even available online.
No need to despair if you don’t have them, though. You can determine the general location of your sewer lateral – good enough for planting purposes -- by following these three steps:
Find the point where the lateral leaves the house by locating the clean out.
Find the point where the lateral leaves your property and crosses into the street by:
Locating an “S” or other similar mark in or on the curb.
Locating a second cleanout at the property edge, in the sidewalk or roadway. This cleanout may be under an access cover marked with an “S” or “Sewer.”
Draw an imaginary line between the two above points – sewer laterals normally run in straight lines.
What to Plant, What Not to Plant
Once you’ve determined the general location of the lateral on your property, you should avoid planting – or maintaining – any plants, bushes or trees that are likely to grow into or otherwise foul your lateral. And, depending on the species of tree involved, the “safe” distance from your lateral varies. For example, roots of some Poplar trees have been known to reach into sewer lines nearly 100 feet away.
Planting appropriate types of trees is of critical importance. Tree roots tend to grow toward sources of water – including sewer pipes. If you're making additions to your home's landscaping, you can save yourself headaches and money by choosing trees with deep root systems.
In particular, avoid planting trees with shallow, spreading root systems near your lateral.
Tree roots, in many cases, mirror somewhat the tree’s above-ground canopy. But, some particularly ambitious trees can extend roots far beyond the limits of their canopies as they pursue water sources.
There are a number of “problem” trees that should be avoided. These include poplars, willows, figs, rubber trees and large eucalyptus trees. Two of the more troublesome trees are the fruitless mulberry and the Modesto ash. For some information on what to plant and what to avoid, click here (link).
More Sewer Smart Planting Tips
After you select a tree, follow proper planting procedures. Be sure to dig a deep enough hole. If your hole is too shallow, the tree's roots will be more likely to spread horizontally making it more likely that they’ll meet, and possibly penetrate, pipes.
There are other reasons to plan before you plant. Trees in the wrong places can also wreak havoc with your homes foundation, driveways, sidewalks and other structures.
More Sewer Smart Planting Information
For more specific information on desirable and undesirable plantings in your area, contact your city’s public works department or your local sanitary district.
Your local nursery may also be a good source of planting information.
Additional information can be obtained from the University of California Cooperative Extension program at https://ucanr.edu.
The International Association of Arboriculture offers a lot of great information on tree planting for homeowners. For specific information on trees and utilities, go to: https://www.treesaregood.org/treeowner/plantingatree.
For an extensive guide on tree selection, visit Cal Poly’s https://selectree.calpoly.edu and select “low” for Root Damage Potential along with the other tree attributes you seek.