Originally Posted by atthelake
Wouldn't that be a inline check valve (one-way valve)? That's what it looks like to me. Regardless, don't take it apart.
Your clean outs should be approx 4-8" inches off the floor and appear to be at a 45 dgeree angle.
Kinda looks like a check valve to me too (but I'm in the natural gas business so not positive).
I've had my rental mainline cleaned out a few times already. Mainly due to tree roots coming in. As long as you maintain (yearly cleaning), you might be OK. I've used the "claw" type cleaning and the hydropressure cleaning. Can't tell you the better one but the big thing is maintain. If the roots get too big, it opens up the hole bigger and then you may be looking at a new line.
Also, when done, send a camera down it to see what's going on. I think tree roots are pretty common....