[Tidybuoy]

I had a similar problem last year. Started with a slow shower drain and occasional plunging would help but finally it backed up in the kitchen too.

I called a plumber that used a power snake in one of the cleanouts. Fortunately, my house had a clean out at the street but if that wasn't there, there are several cleanouts that can be used (including the vents on the roof).

The plumber pulled out about a foot of tiny roots that looked like the small roots you would see on the bottom of a potted plant from the nursery. Although the roots are tiny, they are enough to catch things like toilet paper and other debris and eventually cause a clog.

The plumber told me that I should add about 1/2 cup of copper sulfate (can get at a hardware store or pool supply) every month to the toilet closest to the main line. Copper sulfate will kill the roots but will only kill for about a foot past the pipe so it doesn't kill any of the trees.

I haven't had any problems since and it was a $70 fix.