Hi guys, need some info or run by u guys my plan for an add on for a single bath and kitchen sink. Ill start at end of run- 3" vtr w. 3" vent ell,3x1.5 wye on horz. to 1.5" trap for tub,3x2 wye on hrz. for 2" floor drn. w. trap,3x3 wye w. 1/8 bend on hrz. to 3"ell up to wc,3x2 sant. tee vert. for washer sp,3x2 sant tee vert. for lav.,about 14 feet down stream back to back 1/8 bends to offset drain to get 3x1.5" sant tee vert. in block wall to catch kitchen sink drain and 1.5" vtr . All on 1/4" pf slope out wall to 3x4 red. to 4" main co in front yard about 4' from front wall.My diggers dug my ditch all 17" deep and trap weir to top of slab will be 20",looks like my lav. vent will be about 6'3" from my 3"vtr,this is my concern.Its my first underslab job and I only get one shot so I dont want to cover it or call inspector until im sure. Any help???