I have two under the slab horizontal waste lines intersecting at 90 degrees to each other. The drawing calls for a "drop connection" between the two for the connection. One line is has an invert 32" above the other lower line's invert. How is this drop connection achieved? Do I install two 45 elbows on the higher line and roll them to intercept a proper waste TY fitting off the top? Or do I make a stack between the two and vent the top? Not sure how to do a "Drop Connection". Sloping the two lines at a common intersecting invert does not work do to opther underground interferences.