The intrusion of roots into discharge waste pipes is a major maintenance challenge for the homeowner as well as for contractors and the owners of industrial and municipal sites. The growth of root mass inside sewer lines will block the discharge of wastewater resulting in backup into homes or buildings. The damage caused by the backup can be costly to repair and certainly troublesome. Unchecked root growth can also cause deterioration of pipe and pipe joints, underground pipe structures and pipe connections to the main sewer line. Therefore, an effective root control program is essential.

Roots

Subterranean roots serve several functions for trees including anchorage in the soil, the absorption and transfer of water and nutrients into the main core of the tree and, to a lesser extent, the storage of nutrients. The direction of root growth is determined first by gravity and, second, by water. Root hairs are fine hair-like projections found on the surface of roots, which find their way into drain lines and sewer pipes. They enter through either small cracks or openings in the pipe or pipe joint. Once inside the pipe the root hairs continue to grow and mature eventually forming a root mass. Of the vast subterranean network of roots and root hairs, only small percentages actually protrude into and effect underground pipes. Thus, the mechanical removal of the root mass and root hair within the pipe can be done without damage to the total tree structure.

Removal and Control

The destruction of root hair growth in pipes can be accomplished by mechanical removal. Mechanical removal of the root ball blockage does not prevent the recurrence of new growth. In contrast, chemical technology, which is primarily based on herbicides, has advanced to the point where either in combination with mechanical removal or by chemical means alone, the root mass can be removed and future growth retarded or eliminated. Continued application of the appropriate chemical will degrade any remaining root masses, destroy root hairs remaining in the pipe and effectively eliminate future root growth in the pipe. A note of caution, the timing involved in the combined use of cutting tools and a chemical is critical. Cutting removes the roots and root hairs through which the chemicals are absorbed. After cutting roots will secrete a fluid, which hardens and covers the cuts caused by the mechanical process. This hardened fluid and the absence of root hairs removes any pathway through which the chemicals can penetrate the root system in the pipe. To use the combination of a mechanical and chemical approach, the chemical should be applied immediately after the root mass is cut or wait a period of 3-6 weeks, at which time sufficient new root hairs will have emerged to provide a pathway for the chemical. If only a chemical approach is utilized, the initial application will destroy the root hairs and begin the process of degrading the remaining root mass. The degradation process may take weeks depending on the nature and size of the root system. It is also important to begin the treatment as part of a preventive process, whereby the treatment process begins prior to blockage, i.e. typically in spring and in the fall. The chemicals employed are non-systemic herbicides, therefore present no danger to the tree system as a whole.

Chemical Approaches

There are a variety of chemical approaches available to the contractor, homeowner or building owner. The most significant ones are based on the use of known and accepted herbicides as the active ingredient. They differ on the basis of the herbicide used as well as in the requirement that in some cases sewer maintenance professional apply the treatment. The following describes the chemistry and function of some of the more widely used chemical root control technologies.

Copper sulfate is the most common herbicide used by the homeowner and is an EPA registered product. The copper sulfate is applied by flushing a significant quantity, usually 2 to 4 lbs., into the drain line through the toilet that is closest to the discharge line or through the discharge line clean-out plug. Drain waste discharge lines are usually partially filled with water and the root hairs and root balls are commonly in contact with that water. Once flushed through the toilet, some of the copper sulfate dissolves and is taken up by the root hairs, while the larger crystals become enmeshed in the root mass and provide a longer lasting treatment effect. The copper sulfate should be applied during periods of low water volume flow in order not to prematurely flush away the product or dilute its concentration. The copper sulfate will kill the root hairs upon contact and overtime the larger root ball. Copper sulfate will not remove mechanical obstructions, grease or other matter not related to the root system.

Copper sulfate will not harm trees or shrubs, but will kill and decompose the root in the line. Treatment rates vary from household to commercial and municipal systems. State laws prohibit the use of copper sulfate in sewer systems in Connecticut and certain counties in northern California. Because copper sulfate is considered toxic to wildlife and aquatic plants, federal law prohibits its use or discharge into rivers and waterways.

Dichlobenil is an aquatic herbicide approved by the EPA that kills root systems within an hour of contact. Dichlobenil has been used to control aquatic weeds for many years and due to its low water solubility has little effect on microbes or bacteria. Dichlobenil has also been packaged with a variety of foaming agents and surfactants in order to increase the absorption efficiency of the dichlobenil by the root system. These agents include sulfamic acid, whose alkali derivatives have been identified as being poisonous to woody plants and surfactants, which help the herbicides cling to and penetrate the root hair system. Dichlobenil systems are available through professional sewer maintenance personnel or through common retail outlets. There are no state regulations, which prohibit the use of dichlobenil based systems.

Metam Sodium is a multi-purpose soil fumigant, which is particularly effective against seeds and new roots as well as nematodes, fungus and weeds. It is hazardous to handle and can only be used for root control by licensed, professional personnel.

Miscellaneous chemicals also make the claim to be effective as root control agents. These include strong acids and alkali products, such as drain cleaners, which destroy the tissues and cells of woody plants and trees. These are not registered by the EPA and also have only a temporary impact due to the short residency time the chemicals spend in the root ball area.

In summary, quality root control depends on the proper diagnosis of the problem. For example, is the blockage partial or total? What type of root system is at the cause of the problem? Whatever course of action you choose, timely and consistent treatment is the only way to ensure that the problem remains under control.

References:

Copper Sulfate for Root and Fungus Control, Phelps Dodge Booklet No. 12.

The Cleaner, "Killing and Decaying Tree Roots", February, 1991; George Tobias

The Cleaner, "Getting to the Root", July 2002, Parke Raffensperger.

Root Control, Harford County, Maryland, www.co.ha.md.us/dpw/ws/root.html.

Van Nostrands' Scientific Encyclopedia, 5th Edition, 1976, pg. 1943.

Metam Sodium Taskforce, www.metampsc.com/whatisit.htm.

Herbicide Handbook Seventh Edition, 1994.