Fixit: Before planting tree, locate sewer line

By KAREN YOUSO, Star Tribune

Last update: September 17, 2008 - 9:44 PM

Q I'd like to plant some trees in my yard but I'm worried about the roots reaching my sewer line and causing plumbing problems in the future. How can I find out where the sewer lines are in my yard? Is there a safe rule of thumb for tree-planting so that the roots will not encroach on sewer lines?

A To locate a sewer lateral (that's the sewer line that runs between your house and the main line in the street), try contacting your city offices.

In Minneapolis, for example, Utility Connections (612-673-2451) will tell you where your service taps into the main sewer line. Your sewer lateral would run from that point to the cleanout in your property.

Although the roots of a tree reach far beyond the trunk, they're mostly in the first 12 inches of ground. That's higher than the sewer line. However, don't plant a tree directly above or near a sewer line. Tree roots like moisture and disturbed soil, both of which can be found around a sewer lateral, especially if it's the old clay-tile version. They tend to crack or separate at the seams over time. Roots attracted by good growing conditions enter these spaces and clog the line. This is less of a problem with the newer PVC lines and roots aren't strong enough to break into piping, but still avoid planting over the sewer line.

Before you dig a hole for the tree, remember to call 811. That will connect you to Gopher State One Call, which will request that the appropriate utilities contact you as to where gas and electrical are buried in your yard. IMPORTANT: This does not include private lines. Those would be gas lines to a grill, electrical to outbuildings, pool and landscape light, underground sprinklers, etc.

And don't forget to look up. Unless a tree's mature height is less than 15 feet, don't plant under or near overhead lines or cables.

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