I am in a situation where I need to connect a 1 1/2" section of galvanized pipe to a 1 1/2" section of ABS pipe. This joint is to be concealed behind drywall. Does the UPC allow for concealing of this type joint? It is for the vent line to my washer. I am uprgrading the trap and standpipe to 2", and as the washer is the only appliance on this paticular vent, I am trying to keep it at 1 1/2"