During drought conditions and in winter, tree roots travel long distances in search of moisture. As a general rule, tree roots will extend up to 2.5 times the height of the tree and some species of trees may have roots extending 5 to 7 times the height of the tree.
Root Growth Control
The common method of removing roots from sanitary sewer service pipes involves the use of augers, root saws, and high pressure flushers. These tools are useful in releasing blockages in an emergency, however, cutting and tearing of roots encourages new growth. The effect is the same as pruning a hedge to promote faster, thicker, and stronger regrowth. Roots removed by auguring are normally just a small fraction of the roots inside the pipe.
To augment the cutting and auguring methods, there are commercial products available that will kill the roots inside the pipe without harming the tree.
The use of products such as copper sulphate and sodium hydroxide are not recommended because of negative environmental impacts on the downstream receiving water. Also, these products may kill the roots but they do not inhibit regrowth.
The more modern method used throughout Canada and the United States for controlling root growth involves the use of a herbicide mixed with water and a foaming agent. The foam mixture is pumped into the sewer pipe to kill any roots that come into contact with the mixture. New root growth will be inhibited from three to five years after the treatment according to the manufactures.