Homework: Keeping tree roots out of sewer lines

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An earth auger with two extra pipe sections will allow you to drill a hole up to 8 feet deep. The hammer is shown for scale. Photo Credit: iStock

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There are countless older homes with ancient clay pipe sewer lines extending from the houses to city sewers. These clay pipes, with their mortar-filled joints, are notorious for allowing tree roots into the pipes. When that happens, the tree roots feast on the slurry of organic debris in the pipes, grow to freakish sizes and eventually clog the sewer line. But there's an easy way to prevent his from happening.

You can watch a short video showing how to prevent tree roots from invading sewer lines by going here: nwsdy.li/atb


Make a trip to your local sewer department and ask to see the maps of your street. The staff should be able to show you the location of the sewer tap in relation to the corners of your property adjacent to the street. Ask them how deep the sewer is in the street at your house. Locate the sewer clean-out fitting in your basement that almost always indicates where the building drain exits your home. Your outdoor sewer line runs between this point and the sewer tap at the sewer in the street.


Purchase or rent a 2-inch earth auger. This is a large, hand-powered drill that you twist into the ground to create a 2-inch-diameter hole. Before using it, call 811 to have your underground utilities marked in your yard. You don't want to drill through natural gas, electric, water lines, etc.


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Purchase 10-foot lengths of 1 1/2-inch PVC plumbing pipe, 1 1/2-inch female adapters and threaded plugs. Buy 25 pounds of copper sulfate crystals from a hardware store or online merchant.


Use a string between your house and the street to find the above-ground location of your sewer line based on what you discovered in Step One. This string will ensure you drill holes in the soil above your sewer line.


Sewer lines slope from your house to the sewer line in the street. You can determine the depth of the sewer line as it leaves your house based on how much lower your basement floor is than the ground outside your home. Add 16 inches as the sewer line must pass underneath the foundation footer of your home. Estimate the top of the sewer line as it passes underground using this information and what you gathered from the sewer department.


Using the hand-powered auger, drill a series of holes spaced about 4 feet apart along the string line under any nearby trees that are close to the sewer line. Stop drilling when the bottom of the hole is about 2 feet above the top of the sewer line.


Insert a length of the PVC pipe into the hole, glue on the female adapter and make sure the top of the female adapter is flush with the top of the soil.


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Pour into the pipe(s) one pound of the copper sulfate crystals. Add one or two gallons of hot tap water into the pipe to dissolve the crystals. Add more crystals and water each month for a period of three months. Always screw the tiny plug into the female adapter to prevent the pipe(s) from filling with debris.

Summary: Copper is a natural element that's an effective biocide. The hot water dissolves the copper crystals and carries the copper into the soil that surrounds the sewer pipe in your yard. When tree roots attempt to grow into this soil, they're repelled by the copper. The tree roots then just stay in the soil above the pipe instead of getting inside your sewer, where they would otherwise cause havoc.

DEGREE OF DIFFICULTY: Four hammers out of five

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