I have not found the same issue since reloading the game.
Just like the title, when water enters from the right side of the shower, the water disappears. I did not know the detailed process because it was found late, but at first there was a liquid valve. I tried to remove the valve, but the same problem occurred. Upside is okay when I tested. I have not tried the other direction. (included save file) I have not tried the same situation in a new game. When I poured water from the right side of the shower two or three times in the attached save file, the water continued to disappear. I hope you have a pleasant development. Pluming Error.sav