Q: We moved into our home about three months ago, and this week we had a professional inspection of the septic system. The septic contractor found a large mass of tree roots in the tank and recommended that we flush about 10 pounds of copper sulfate down the toilet. He said this would eventually kill the roots. I'm concerned that the copper sulfate won't get rid of the roots or that it might harm or kill the two large trees in my front yard. What do you recommend?

A: Your septic contractor has advised you correctly. Tree roots can be removed mechanically, but copper sulfate is a lot simpler and much less costly. Copper sulfate crystals can be flushed down the toilet to destroy existing roots or discourage the growth of new ones. The effect is not immediate, but when copper sulfate makes contact with tree roots, it gradually kills them and causes them to break off and decompose. Be aware, however, that this is not a permanent solution. As long as trees are located near the septic system, roots will continue to invade. Therefore, periodic treatment with copper sulfate will be necessary to maintain a root-free septic tank. By the way, trees are not typically harmed by copper sulfate.

To protect the bacterial environment in your system, no more than two applications of copper sulfate per year are recommended. For best results, schedule the application to allow minimum dilution and maximum contact time. For
example, you could flush the copper sulfate just before leaving on a weekend vacation.

The recommended dosage rate for copper sulfate is 2 pounds per 300 gallons of tank capacity. Since your contractor recommended 10 pounds of material, your tank capacity must be 1,500 gallons. Be sure to confirm this.

By Barry Stone