I have a shower at the last point (highest on the slope) of my drain line in my master bath. I am increasing the size of the shower and removing the wall that contains the pipes and and the drain vent. I need to know if the vent is necessary based on the configuration, or could be eliminated. It will be exceedingly difficult to reroute due to duct work and other constraints. The bathroom presently contains the shower, two lavs, a bathtub and toilet (lowest on the drain route)all with their own dry vents connected to the main stack. Please help.