Galvanized waste rules in highrise building

I am managing a 15 story highrise built in about 1975. My question is with 2" galv for sink waste lines and a 1/2" fall per foot , how does that take place when you cant really bend the pipe on a 10' run to fall 5"s or ???

Another question is when a line horiz. line goes into a riser line does it use a straight tee or do they make a sweep tee? The drain cleaner guys ran a snake but said it was not going down the line but instead going up the vent when it came to a tee. This does not make sense to me in this day and age. Would not the tee need to be a sweep to insure the snake always ran down hill?

Help

That system is installed with "Durham" fittings. They are tapped with a built in 1/4" per foot slope. To get more slope, we cut "crooked threads" on the pipe. The tees ARE sweep tees, but it is only a "nudge" in the proper direction. The snake SHOULD go downward, but there are several factors that could allow it to go up the line instead. One of them being if the pipe is stopped up exactly at the tee. They may not be using the right snake.

Does your code require 1/2" per foot? Threaded cast iron fittings are built with "slope" . Probably at 1/4" per foot

Just guessing at slope since it used to be 1/8 for 4" 1/4" for 3" so I assumed doubling for 2"

Just learning. Highrise stuff is different then residential.

Thanks to all

1/4" for up to 3". 4 inch can be 1/8", but the fittings would normally be tapped for 1/4".