The sink drains have become blocked in a duplex apartment. There is a bathroom on either side of a shared wall, with each sink belonging to a different living space in the duplex. There is a straight pipe between the sink drains: if I remove both traps I can see through it. The setup is something like this:
That tee in the middle is inaccessible - it is between two walls and above the subfloor. Running a snake from a sink obviously doesn't work, and it would take a lot of liquid plumber to fill up both traps and the bottom of the horizontal pipe.
Under the house, there isn't any access that I can see. I'm not a plumber, though, so maybe I'm missing something. Here's a mediocre picture of the pipes (the purple circle in both images represents the same elbow):
Any suggestions would be appreciated!