: : This 20% is new to me. Had to have been added within the last 15 years. Why I couldnt begin to guess, it never made it into our state code which is almost a carbon copy of the National Standard Code. : : But to answer your question the best I can would be any branch vent could run horizonally as long as it is a min. 6 above the flood rim of the highest fixture its serving, back pitched to the drain and is within the developed lgth. of the chart for max. distance.: Oh well, thanks anyway. What state are you from? Im from Arkansas, and our code is a composite of the national and sbcci code, i wish the state would just adopt one of them and run with it. When the two are put together there are some gaps that are hard to figure out. Ed.Ed, Im from N.Y.(western). you state the 20% came from the National Std. Code. Maybe some one out there could enlighten us on this change as to when & why. The only thing that would make any sense of this on vent stacks would be limiting the amount of flat venting below the flood rim. once you are 6 above the flood rim it wouldnt matter.
