Q&A / 

Sewer Lines and Tree Roots

DEAR TIM: The sewer line in my house recently backed up. The plumber who cleaned out the line discovered that tree roots were the problem. I have seen products that you flush down the toilet to solve this problem. Are they effective? Is there a better, more long term solution? I really don't have the money to install a new sewer line. Chuck S., St. Cloud, MN

DEAR CHUCK: Tree roots in sewer lines are probably one of the top ten plumbing problems, especially in older homes. Mother Nature has equipped many trees with sophisticated sensing capabilities. The trees send out feeder roots in all directions in a search for both nutrients and water. The trenches that contain sewer lines rarely contained compacted soil. Roots are naturally drawn to this disturbed soil.

Here is a wonderful hand-powered earth auger. It drills a two-inch diameter hole with ease.

Here is a wonderful hand-powered earth auger. It drills a two-inch diameter hole with ease.

Tree roots enter sewer pipes through small cracks in the joints between individual pieces of pipe. Old clay pipes often had the joints packed with mortar. Over time this mortar can develop cracks or shrinkage cracks can develop as the mortar hardens. If tiny feeder roots discover these cracks they enter the pipe and continue their search for moisture and food. Once inside the pipe the roots enlarge and gorge themselves on the plentiful supply of water and food. I have actually taken out grotesque roots that have been over ten feet long and nearly one inch thick in diameter.

The root control/elimination products that flush down a toilet do little to solve the problem in my opinion. Water flow in a typical sewer pipe only fills a small percentage of the bottom cross section of the pipe. The chemicals often only burn those portions of the roots that actually contact the water flow. Some of the chemicals are drawn into the root system but not enough, in my past experience, to completely wipe out the roots. The tree continues to grow and send roots out to take advantage of the underground oasis.

I have solved this problem for customers and at an old house I used to own. Your best chances of success will happen if you can find a company that sends a small camera into the sewer line. By looking at a video monitor, the best camera operators can pinpoint the exact location outside where the roots are entering the pipe. What's more, with electronic sensing equipment the professional can tell you the depth of the sewer pipe below the surface of the ground at this location. Armed with this data, you can permanently solve the problem.

Using a simple earth auger or large drill, you will drill a vertical hole down towards the sewer pipe. A 2.5 inch diameter hole works best as it provides plenty of room to insert a standard schedule 40 1.5 inch PVC pipe into the hole. Stop drilling when the hole is about 24 to 30 inches above the top of the sewer pipe. Slide the pipe into the hole and glue a threaded female adapter equipped with a plug onto the end of the pipe at the surface. Make sure this is flush with the soil so that lawn mowers do not cut it off.

I am ready to get to work. I made sure no underground utilities other than the sewer line were in my path.

I am ready to get to work. I made sure no underground utilities other than the sewer line were in my path.

If you can't find a company with a sewer camera, use municipal sewer records to locate your sewer tap and try to estimate where the sewer line might be. Insert a number of PVC pipes in your yard hoping that you spot them above and near the sewer line.

Pour copper sulfate crystals into the pipe. Try to fill the pipe halfway with these crystals. You can buy them at many plumbing supply houses, feed mill centers, and or old hardware stores. Some home centers may carry them. Immediately pour hot water into the pipe until it flows out the top. The hot water will begin to dissolve the copper sulfate and then this solution will begin to seep into the soil above and around the sewer pipe. Tree roots do not like soil that has been treated with copper sulfate and they will avoid it completely. Add crystals as needed and pour hot water into the pipe every four months or so to stop those pesky sewer backups!

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