Question
We have a large and old conifer to the side of our driveway.  Our adjoinging neighbours now say that the conifer is causing their drainage problems. I was wondering what kind of root system the conifer has.  The tree is not causing any cracking to our driveway.  As I am in Sydney we have had long periods without rain and was wondering if their old drainage pipes and joints are cracked therefore the roots are searching for water.  Any assistance and guidance would be appreciated.  Thanks Nicole Field


Answer
Tree roots do not cause drains or sewer pipes to break, but they will invade and clog drains that have pre-existing cracks and resultant leakage.
Drains are usually six to eight feet below ground level, while tree roots grow almost exclusively in the upper two feet of soil, because they not only need nutrients, but also oxygen to survive. When drains leak, they provide oxygen and nutrient rich water deep in the soil, which allow tree roots to grow deep into the soil and get into the already cracked drain pipe.

Sewer pipes especially the older clay or felt type can be invaded by the roots of many trees. This may clog the sewer pipes and cause back up and will need to be rooted out. Newer PVC type sewer pipes will not be effected.

Tree roots are often blamed for blocking sewer pipes; however, tree roots only penetrate sewer pipes that were previously damaged by other factors such as poor construction, aging and soil settlement.

When the small exploratory roots come into contact with cracked or leaking pipe, they are stimulated to grow vigorously often into the damaged pipe.

The combination of roots and solid wastes will usually develop into a partial or complete blockage of the sewer line.

The following is a list of treatments available to homeowners to correct blockage problems in the sewer line.
Plumbing contractors have equipment for removing blockages from the sewer lines. This method provides short-term solution.
Chemical root inhibitors are available to kill roots.
Copper sulphate can be used to kill roots within sewer lines.
Sewer pipe liners are inserted into the sewer and positioned into the damaged area of the pipe.
Replacement of the sewer pipe in severe cases is the only effective solution.