Best fix for tree roots in sewer line
Experts assess 4 options
Bill and Kevin Burnett
Q: My 30-foot ornamental plum tree has sent its roots into the 1890s clay tile sewer line. It needs to be snaked about twice a year. The tree is at the front of the house, about 15 feet back from the sewer opening in the sidewalk.
Would you please give me your opinion of the four solutions that have been proposed?
1. Dig up the entire sewer line, about 70 feet and under the concrete garage floor, and replace with new cast-iron sewer line.
2. Install a “trenchless” line, digging holes at each end of the sewer and then pulling a new plastic liner through the existing pipe. The city plumbing inspector says this type of repair is allowed.
3. Partially replace the line, extending 10 feet to either side of the tree.
4. Cut down the tree (it is on private property, so no permit needed) and dig out all the roots.
A: The first order of business is to understand why the sewer line has become part of the tree. It has to do with the joining of the clay pipe and the tree’s constant search for water and nutrients.
Antique clay sewer lines consist of 3-foot sections of clay pipe with a bell joint at one end. The pipe was simply laid in the trench with the non-jointed end slid into the bell. At best, the joint was packed with a little mortar around the outside, which quickly deteriorated. These joints leak.
Because there is no pressure in sewer lines, this is not such a big deal until tree roots find their way into the pipes. Then it’s Roto-Rooter time — again and again as the roots are pruned and then regrow.
With this background, here’s our take on each of your possible solutions. We’ll take them out of order.
Don’t cut down the tree. A 30-foot tree has been in the ground for at least 15 years. Kevin has an ornamental plum tree in his yard and he and his family get a great deal of pleasure from the blossoms it produces every spring. The overall value of your property is likely to diminish if you take out the tree. In our view, this course of action is penny-wise and pound-foolish.
Replacing the line 10 feet on either side of where you think the roots are entering is not the solution, either. It will probably help for some time, but eventually the tree roots will migrate to the portions of the remaining clay tile and you’ll be stuck with the same problem.
Normally we’d opt for No. 1: replace the entire line with no-hub cast iron or glued ABS or PVC sewer pipe if codes allow. But we’d hate to see you have to cut into your garage floor to replace the pipe.
So, we like option No. 2 the best. We can see a couple of potential problems, though. First, because you’re using the old pipe as a casing, this will necessarily reduce the inside diameter of the pipe that is installed. Make sure that the fix will perform. We’d hate to see you go to that expense to be left with more trips from Roto-Rooter because the pipe is too small.
The second potential problem we see is the new pipe getting hung up as workers try to pull it through the old clay pipe. Without a doubt, the line has settled over the years and some of the joints may be cracked and offset, so pulling the new pipe through could be a dicey proposition.
Also, we’d be dead shocked if the tree roots hadn’t migrated to other joints, creating a possibility that the new sleeve might get hung up on a mass of roots.
Another option you may consider is to replace the clay sections with cast iron or plastic from the city sewer to the point where it goes under the garage slab. Providing there are no big trees or shrubs between that point and where the sewer exits the house, this might be your best option.