How to open up T-shape clogged drain pipe?

[Ting Liu]

I have a two-unit apartments. The two apartments are side by side. Their kitchens are next to each other separated by a wall. The two kitchen sinks are connected by a T-shape drain pipe.  The T-shape drain pipe is clogged. I tried to unclog it with a 30-foot snake.  But the snake went from one apartment to the other apartment, but unable to get into the bottom part of the T-shape. I think the top of T-shape is flat. If it is a Y-shape, snake should be able to get into the bottom pipe.  I have also poured a large bottle of Drano into the pipe.  But no luck.  Besides opening the wall, is there any other way to solve the problem? BTW, the pipes are all buried in concrete wall. If I have to open the wall, is there a good way to do so. Please advise. Thank you!