Fall brings sewer line intrusions

Cracks and weak joints provide a nourishing haven for tree roots.
Sunday, September 21, 2003 | 12:00 a.m. CDT; updated 10:33 a.m. CDT, Saturday, July 5, 2008

Autumn is a time for football, fallen leaves, and in some older Boone County homes, a tree root clogging the sewer line.

Fixing the problem is, at minimum, a messy nuisance, but in worst-case scenarios can cost hundreds of dollars.

This is a particular problem in October and November because tree roots grow faster when soil moisture and temperature are prime, MU associate forestry professor Steve Pallardy said.

Tree roots encroach into sewer lines when they contact moisture from leaks or weakened joints in a homeowner’s service line, which connects to the city-owned main. When a growing root reaches water and nutrients, it will make offshoots to absorb even more of the sewer’s available nutrients, Pallardy said.

Most Missouri sewers built before the late 1970s are made of clay, which can crack and leak. They are laid in 4- to 5-foot lengths, so there are many joints that could leak, Columbia Sewer Utility Manager Terry Hennkens said.

One Ashland homeowner, David Mars, said the hidden nature of tree-root growth first became apparent after he planted a bald cypress near his 50-year-old home.

“Tree roots are incredible, imperceptibly growing,” Mars said, referring to how they can back up drains and flood basements.

Sewer cables are the primary tool for keeping root intrusions at bay, Columbia plumber Russ Duker said. Machines, whether manual or electric, extend a steel cable into the sewer line until it becomes entangled in the root mass, then bring it out, tearing apart the intrusion.

Duker, a manager for Mastertech Plumbing, said it costs about $95 to have a plumber clear up to 100 feet of line with an outside access point. Costs rise, however, with complications.

“It depends on the access inside and outside — and white carpet,” Duker said. “You do something like that on white carpet, it costs even more. It’s such a messy job that if it’s done on the inside, you have to take extra cautions to protect the interior of the home.”

Bill Spry, co-owner of Lindsey Rental, rents manual sewer cables and electric cable machines to people who want to clear drains themselves. He said that manual machines rent for $16 a day; electric models cost $27 for two hours.

After a tree root finds a crack in a nutrient-rich sewer, it will continue to grow roots even after it’s cut from the pipe, Hennkens said. “Trimming roots is like pruning a bush,” he said. “It will sprout branches. If you prune roots they will sprout more growth.”

The biggest root intrusion Duker saw measured 16.5 feet long and 4 inches in diameter, as big as the average resident’s sewer line.

After roots are cut free, plumbers will use a herbicide foam that kills the roots for the time being. The permanent solution is to line the pipe with a protective coating or replace it. Replacing one length of pipe with chronic root problems, however, can cost $500 to $600, depending on the line’s depth and other obstacles on the property, Duker said.

Pallardy said one tree that people should not plant in their yard in order to avoid such problems is the weeping willow. It responds strongly to moisture, and its roots spread far beyond its drip line.

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