Installing PVC Casings to Stop Tree Root Growth
Stopping tree roots that invade a sewer line requires a little investigative work. You somehow need to find out the position of the sewer line. The older the house is, the tougher this can be. Why? Because old sewer lines were built using 3 or 4 foot lengths of clay pipe that can easily be installed in sweeping curves, not necessarily a straight line. Your best bet is to hire a company that can send a camera into a sewer line and use an electronic sensing device to determine the location and depth of the sewer line as it passes beneath the ground.
Sewer Department Records
If your indoor plumbing connects to a municipal sewer system, I always start the process by visiting the sewer department. Most have good records and they can tell you the location of your sewer tap. This distance is measured quite accurately from the center point of the nearest manhole. Most sewer taps then extend at a 90 degree angle from the main sewer towards the property line. From here it can get a little tricky. Take my sewer line for example. The developers of my subdivision decided to save money. Instead of digging separate trenches for each house, they dug one wide sewer tap trench for two adjoining lots! My sewer tap and my neighbor's are next to one another right at our shared property line. I had to install a 45 degree elbow followed by a 22.5 degree elbow immediately off the tap to be able to get to the center of my lot. Once there I had to install the same fittings to be able to head in a straight line back towards my house. See the problems? And my house is only 15 years old! But armed with sewer tap records, you can at least have an idea where the sewer line ends at the edge of your property.
Drilling
If you have any buried wiring, gas lines, water lines, sprinkler lines, etc. be sure you get these marked if possible. A sharp earth auger can damage these lines and if it is electric or gas, you might cause serious injury or death! Be sure to use the right sized auger for the job. I prefer to use one that drills a 2.5 inch diameter hole, since 1.5 inch diameter PVC pipe has a 2 inch outer diameter. You want the hole a little bigger than the pipe so that the casing slides into the hole with minimal resistance.
Location and Depth
If you can determine the exact entry point of the roots into the sewer line then you can spot a casing pipe directly over that location. If you can't find the exact spot, you may need to install a series of casings spaced at 6 foot intervals along a stretch of sewer line that is under or adjacent to the tree or trees that are causing the problem. Remember to stop the casing about 18-24 inches above the top of the sewer line. You want gravity to help you distribute the copper sulfate solution. Drill too deeply and you are simply wasting your time. Keep in mind that the sewer department records will tell you the maximum depth of the sewer tap. Use this information and the estimated depth of the sewer pipe as it leaves your house to get an idea of how deep the sewer line is as it makes its way across your yard.
Access
The top of the casing needs a simple threaded plug that screws into a female adapter. This allows you to add copper sulfate crystals and hot water at periodic intervals. If you don't want to see white dots in your yard, consider painting the plug green to make it blend in with the grass. It is also a good idea to create a little map of the casings, measuring the center point of the plug from two fixed points of your house. This triangulation method allows you to pinpoint the casing if it should sink into the soil over time. Place a copy of the map in a plastic freezer bag and attach this bag to the water line in your basement or utility room.
Repeated Treatments
The copper sulfate will need several months to work initially. You then might want to add more every 6 months.
