That works but do you really have the height for that under the slab? There are also much less convoluted patterns you could use, such as the one Reach4 suggested in post #17.What if I install a Y for the vent between points A (the WC) and B and then run the vent to the nearest wall (which is behind the toilet)...this requires reversing the vent direction 180 degrees with some 45's from the Y but I presume that's acceptable as long as I maintain a minimum 45 degree slope on the vent, correct?
I assume this is a remodel? Do you have pipe at a ceiling level which is a dry vent through the roof, carrying no drainage? Is the trench shown in the OP still open?