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Knowledgebase record #450

PAL Question

I have several sewer pipes that are getting plugged by tree roots on my grounds. I have used a rooter to remove the majority of the roots and know would like to detour their return by using a chemical called Root Free. It is a Copper Sulfate Pentahydrate. Is this product safe for my trees if used according to label?


Here is a link to information on this chemical from the Pesticide Action Network's database. This link leads to the Material Safety Data Sheet for Copper sulfate pentahydrate.

This product is highly toxic to humans and aquatic life, but should not harm the trees. My question would be whether it makes more sense to remove entirely any trees with invasive roots, and replant with other plants whose roots will not cause trouble with the sewer pipes, rather than use copper sulfate. See information below from UGA College of Family and Consumer Sciences Cooperative Extension Service:

Tree roots can enter sewage and drainfield lines and cause plugging of the lines. Lines should not be placed near trees, and trees should not be planted near lines. Remove tree roots mechanically or flush copper sulfate crystals down the toilet to help discourage or destroy the roots where the solution comes in contact with them. Some time must elapse before the roots are killed and broken off. Recommended dosage rates are two pounds per 300 gallons of tank capacity. No more than two applications per year are recommended. Time the application of copper sulfate to allow minimum dilution and maximum contact time. Copper sulfate will corrode chrome, iron and brass, so avoid contact with these materials. Used in recommended dosage, copper sulfate will not interfere with septic tank operation. Neither mechanical removal nor copper sulfate contact is a permanent solution for tree roots. Remove the trees for a permanent solution to the problem.

Here are some links to more information tree roots and sewer lines and about planting on drain fields:
Tree Roots vs. Sewer Lines from the city of Paso Robles, CA.
Choosing Sewer Safer Trees
Planting on Your Septic Drain Field

And here are some suggestions for alternative plantings:
Landscaping Your Drainfield

If you do decide to go ahead and use the Root Free, by all means follow the directions to the letter, as it is required by law. You may want to check with Seattle Public Utilities Drainage and Sewer Maintenance to make sure that use of this chemical in the sewer system is permitted: 206-386-1800

Keywords: Tree roots, Landscaping drain fields
Date: 2007-05-16

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