So a plumber has diagnosed my drain backup issue as tree roots in my sewer line approx. under the sidewalk about 60' from my house. He scoped and showed me the pictures and cleared with all kinds of tips attached to the snake. From here, I have some questions.
1) My pipe is made of a hard concrete like material, neighbor recently replaced drain line from home to city line and plumbers said it was made of asbestos. If roots already got into the line and I use some kind of root killer every 6mo. Won't the roots that caused the problem still grow slightly in those 6mo and eventually cause a bigger breech in the line?
2) If the line is breeched at the current place, does it stand to reason that the rest of the line could be breeched at some point?
3) Cutting down the tree is not an option, it's in a neighbor's yard and neighbor is uncooperative. City has limitations as well. Is a liner type of repair good or some other form of repair be considered?
4) If you were in my situation, would you use root killer periodically and call a plumber for maintenance every other year at $175 to $200 a pop, or would you bite the bullet and do a repair of the line?
5) If you would choose a repair, would you repair only the section that is an issue now or replace the entire line? (line is about 50 yr old)
6) How much would should I expect each type of repair to cost?
Thanks!

I would cut the tree roots at the property line and replace the pipe with PVC.

hkstroud - thanks, but I can't get to the roots at the property line. It is causing problems under the street and sidewalk about 9 feet underground. May I ask, why the suggestion for pvc? My plumber recommended replacing half of the more accessible drain with polyethylene through some sort of process where they don't have to dig a new trench in my yard and for the deeper portions, to use a resin liner within the existing pipe. I'm not sure why the half half, why not just do the entire thing with a resin liner?

As you have found out copper sulphate kills the roots and retrards growth but will not desolve them. If I were a homeowner and handy with tools I would go down to Rent All and rent a Ridgid K-60 sewer machine. I would ask that they furnish me with a 3" cutter tip to attach on the end of the cable. While you said "main stack" which is the vertical pipe through your roof, I'm betting you meant "main line". Open up the 4" cleanout Tee outside and feed the snake with the cutter tip in. Since most roots get in the line at the raiser,( where your sewer connects into the street sewer) you will have to put out enough cable to make it out to the street. The cutter will cut them up to where you can flush them out with a garden hose. To keep them under control, continue to pour copper sulphate down the line every once in a while. This gets you off the hook, however for a permanant repair you will have to locate the opening the roots are getting in and repair it. To locate the break I mark the cable at the point it augers into the roots. Than I lay it out on the ground following the sewer line. Where the cable ends, that's where you will find your problem. Hope I've helped and thank you for rating my repair. Tom

Plumber is talking about relining the existing pipe. I can't really comment on on the longevity of that process when talking about roots.
Tree roots grow around pipes and push the up, down, or to one side and cause breaks, usually at joints. They then get inside and really start to grow (because of the moisture. Nine feet down is pretty deep for a tree root, most roots are pretty close to the surface. Granted once a pipe starts leaking a root will start grow to it, no matter how deep. PVC pipe is probably the most flexible pipe and would bend to some extent before breaking and leaking (which would be at a joint).

Your choice of course but if you decide to replace I suggest that you have the plumber lay the line, put a couple inches of fill on top. Then take some 1/2 PVC, put a cap on the end and drill some small holes in the bottom side. Turn this up and come up to ground surface, bush it out to 2". That way you could periodically apply some root killer chemicals around the sewer line, since you can't do anything about the tree.
Granted that is not a conventional thing to do, just something to combat the tree roots. Might help, doesn't cost much.

My two cents ...

Once you have roots inside the line - they are there to stay and cannot be removed. Yes, you can control it by snaking the line couple times of year - but if it is in my house, I replace the pipe with ABS or PVC pipe.

Relining is very expensive and doesn't fit every situation.

Sewer replacement is all about excavation. Plumbing itself is not that hard to do nor is it time consuming. See if you can get somebody to dig it up ( by hand or with tractor / bob cat ) and than have plumber to remove the old pipe and to install new one. He will be installing 3 x 20' sections of pipe and 1 clean out. Should not take him more then 3-4 hours to do. You can buy all materials in Home Depot for under $300.00 for the entire job.

Back to you / Milo

Purchase a pound of copper sulfate from your local garden supply house.
Flush it down the toilet. Repeat in 6 months. This will control the roots.
You mentioned realigning the sewer pipe. Let me explain a bit more about my drainage problem and how I repaired it. 54 year old house. The builder used sub standard cast iron in the drainage. The 4" house main was completely ate up on the bottom of the pipe , blocked with roots and welling up in my living room floor. I was sure that the main had broke in two and I would have to jack hammer up the floor and tunnel under the foundation to transition to PVC, pick up the back bath and move the main outside the house but I had to know what was going on under the slab so a friend suggested running a camera down there. There was no distinct break in the main, however,it was completely ate up on the bottom. That's when
Rooter Man of Sarasota and Gulf Coast Florida suggested relining the main, (see image). It took a day to clear the roots and pressure jet clean the main. Next day they came back and relined the main with epoxy. I now have a sewer main that will out last me, (50 year guarantee) and the best part is that I didn't have to, tear up my house and the cost was under half of what I figured to take the main outside around the house. Another bonus was that it was done without tearing up or disturbing my house. When they were finished I kept a piece of the epoxy liner to check it out. It was white and had the same thickness of Schedule#40 PVC.
I was amazed at the equipment RooterMan had outside my place. The equipment he had cost upwards of $100,000.00. Hi tech stuff that took a technician to run it. There were 3 men and 2 trucks to do the job. And it was completed in two days. Lottsa difference from the old days when I went out on a sewer call with a Ridged K-60 Sewer Machine and a ladder to get to the roof vent. I just wanted to point out that there's another option besides replacing drainage that the years have ruined. If your pipes are a candidate for a reline job I strongly suggest you look into it before you decide to replace the drainage pipes. I did and saved a bundle in addition to keeping my home intact. Just thought I would share that with you all. Regards and thank you for rating my answer,.Tom