What is the obstruction in this cleanout interior drainpipe?
I have a drain that backs up after the water is run for about a minute. I ran a snake as far down the pipe as it would go, but couldn't find the clog. I got under the floor and found a cleanout access for that pipe. I opened the cap, looked inside, and saw that there was something that looked like an internal flap that I guess is supposed to direct water towards the drain and away from the cleanout cap. I poked at it, and it appears to be made out of some sort of foam-like material, as it gave a little when I pushed against it.
But what goos is a cleanout access if you cant get into the pipe to clean it out???
Am I just supposed to tear that thing out of there, or what?