I will be moving various bits of soil piping around and have drawn a
blank on fall rates. From a look, old cast iron pipes look to have a
generally steeper fall than modern (smooth) plastic piping [which
makes sense]. Also, soil piping seems to come with either 2.5 degree
or 22.5 degree branch adaptors. What are the regs / practice? Is it
2.5 degrees for plastic and 22.5 for iron?

Thanks,

Mark