Symptoms of a Problem
What constitutes waste for humans is food for plants, and to get it, nearby trees and shrubs send feeder roots through small cracks in concrete tanks, cast-iron or concrete pipes and even plastic pipes, if the joints are compromised. Once inside, they turn into root masses that effectively block the tank or pipes, and you notice this in the house when your toilet begins flushing sluggishly or your drains back up. When the roots invade the pipes in the drainage field, you may notice unusually green grass and healthy vegetation, soggy ground and sewage odors.
Copper Sulfate for Roots
Copper sulfate is one of the most-often recommended treatments for tree roots in septic systems. When they absorb it, roots die, but it doesn't travel very far up the roots, so the plant is usually unaffected. The recommended dosage is 2 pounds of crystals per 300 gallons of tank capacity, usually administered through the lowest toilet in the house. Copper sulfate isn't an instant solution, because it can take weeks for the roots to deteriorate and wash away after they die. Moreover, not everyone agrees that copper sulfate is safe for the groundwater, the drain field or the environment in general. Some communities prohibit its use for root control.
Mechanical Root Control
If your septic system is blocked, you need to control the roots mechanically, and there are a wide variety of tools available for this purpose, although most should be handled by licensed personnel to avoid damage to your system. To handle roots in the septic tank, a specialist pumps the tank, then cuts the roots with pressurized water or a mechanical cutting tool. He may also use a hand tool, such as a hoe or pitchfork, to physically remove them. Mechanical tools -- especially those that use pressurized water -- also work inside pipes, but the specialist usually inserts a camera in the pipes first to locate the roots. Removal of the plants sending the roots is also usually recommended.
Foaming Root Killers
Copper sulfate isn't the only herbicide available; dichlobenil has a long history of use for root control and is registered by the Environmental Protection Agency for general use, which means you don't need a license to use it. It's the main ingredient in a popular foaming product that effectively kills roots in your septic tank. To use a product such as this one, you mix its two parts together in a bucket to initiate the foaming action and then pour it directly into the tank or through a clean-out in the inlet pipe. After the roots die, you wait for them to deteriorate and wash away. To treat the leach field, pour the combined powders into the distribution box, a leach field cleanout, or into the septic tank's outlet pipe, if accessible. Restrict water flow for several hours before and after treatment, to allow the foam to work.