Where to Plant a Tree, Part 2: Water and Sewer Line Proximity
Keeping Tree Roots Out of Your Pipes
A very common problem with trees in residential yards occurs when roots grow into a home’s water or sewer lines. It’s more likely to happen with homes that have older pipes and big trees, but you can avoid a future problem with your pipes by being strategic when you plant new trees in your yard.
Water/Sewer Connections
If you live in Nashville, pipes connect your home’s plumbing to Metro Water Services for incoming water supply and to the public sewer system for drainage. These pipes are typically made of durable PVC piping today, but homes built before the 1990s may have clay or iron pipes if they haven’t been refitted. Property owners are responsible for maintaining the pipes in their yard, according to the Metro Nashville Plumbing Code (chapter 16.12). This means if you don’t know what condition your pipes are in, it may be worth having them inspected and potentially replaced.
Older pipes were made of clay, a wood composite called Orangeburg or cast iron. These materials corrode and crack over time, and when they do, tree roots are able to reach in to take advantage of the water and oxygen in the pipe. While some pipes are buried deeper than six feet, other pipes are as shallow as one or two feet deep in the ground. This means they are within the range of a tree’s root system, which is usually a few feet down (and the bigger the tree, the deeper and wider the root spread will be).
Spreading tree roots can impact water and sewer pipes in your yard if planted too closely.
How Roots Work Their Way Into Pipes
Trees have different kinds of roots: the taproot is the central one that goes straight into the ground from the trunk; lateral roots spread horizontally near the surface and anchor the tree; and feeder, or secondary, roots, which are smaller and thinner, but are the most numerous and spread out at all angles in the ground in search of moisture, oxygen and nutrients.
When a tree is too close to a water or sewer pipe, the secondary roots and their root hairs can find their way into a small crack in the piping or through a leak at a connection. It takes only a couple of these fine roots to work their way in to absorb moisture and air, expand, open the break and extend more roots into the piping. Once they’re in, tree roots can fill up a pipe more and more over time until it's totally blocked. This can lead to low water pressure, drains backing up, interior flooding or leakage in the lawn.
Three Key Factors for Protecting Your Pipes
While you shouldn’t hesitate to plant as many trees as you can fit in your yard, it’s important to do so with some advance planning:
One of the best ways to prevent a future problem is by knowing where your water and sewer lines are located. Water lines are usually somewhere in the front yard, connecting to a water line under the street. Sewer connection lines in Nashville can be in the front or (more rarely) back yard. If you don’t have a blueprint of your property, a plumber can help you locate and inspect your pipes.
If you’ve noticed your neighbors having their pipes changed, but you haven’t, it may be a sign to get yours checked out. Being proactive about maintaining water and sewer pipes and preventing roots from getting into them saves lots of time and potential damage in the future.
Small trees can quickly get big, so a rule of thumb to remember when deciding where to plant is that a tree’s roots will spread out as wide as the crown at maturity. A tree should be planted at least that far away from a water or sewer line to be sure the roots can’t reach it.
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