Vertical plastic joint leak in waste line
I live in a 140 year old house. As usual, plumbing is a conglomeration of materials. I have been hearing dripping through the kitchen wall when water drains from the second floor bathroom. There is a false wall behind the kitchen cabinets and dishwasher. The drain line and water lines run through that space. From just under the second floor the drain vent stack is cast iron. It has a "Y" fitting under the floor and copper line from the fixtures in the bath. At the bottom of the cast "Y" fitting there is a Plastic fitting. The plastic pipe below it goes up inside the plastic fitting. It appears that the joint is leaking where the pipe goes up inside the plastic fitting. This is positioned in such a way that I can't sees how the fitting can be easily replaced. Is there a way of repairing a vertical leak?