Background: We are taking these two walls as part of remodeling. The two walls are marked "X" in the picture of lengths 36" and 84". These walls are located in the first floor directly below our master bedroom and master bath. We have a finished basement on the floor below these walls. We discovered drain pipe and inlet water line running through one wall (36") and it is also a load bearing wall. We confirmed by opening a small part of the sofit, where we located these drain pipe + water inlet pipe. The drain pipes for the master bath sink and jacuzzi are through another wall but they use all share the same inlet water pipe. The master bath shower is directly over the intersection of 36" wall and 84" wall.

The inlet pipe or water line runs from basement to the master bath through this side wall (36"). In addition, the drain from the shower upstairs runs down through this wall. There is a sofit above the wall (84") which we plan to keep even after removal of the wall. Therefore, the suggestion from the plumber/contractor is to keep the sofit and run plumbing through the sofit to the other end and bring it down through the adjacent wall. i.e., "wall A". Then in the basement run the plumbing across the length of 84" wall to connect back to the original drain. In short, instead of a straight drop down we go around 3 sides of the rectangle. We ahve also located a waterline running from water heater in the basement through the wall A.

My concern is (1) whether this will affect pressure in the shower upstairs? (2) Also, drain running all the way through all these walls - is it OK? (3) any better alternative? We have structural engineer to provide drawings to remove the walls. (4) Should I ask him to help with these plumbing lines?

Thanks in advance for sharing your knowledge on how we should proceed.