I have a 50 year old house, and the drain lines are 1-1/2" galvanized steel with cast iron elbows and tees. All drain lines run to a cast iron main stack. I need to replace one of the 1-1/2" galvanized steel pipes that enters a 3" leg of a "Y" that looks like a sanitary tee in the main stack. The old 1-1/2" steel pipe was shoved into the 3" opening in the tee and the space around it was filled with lead (I guess to hold it in place and seal it). I thought it was going to be a simple job to replace the steel pipe with ABS, by just butting a 4" diameter ABS pipe top the cast iron "Y" and connecting it with a Fernco coupler containing a SS sleeve, but when I look into the "Y", I see the ID is reduced to about 2" right before it turns downward. I'm worried that if I just connect the ABS pipe directly to the end of the cast iron collar, the ID reduction will form a small lip inside that will catch debris and have the potential to clog. The old steel pipe was inserted all the way up to the reduction point in the " right before it turns downward. I'm worried that if I just connect the ABS pipe directly to the end of the cast iron collar, the ID reduction will form a small lip inside that will catch debris and have the potential to clog. The old steel pipe was inserted all the way up to the reduction point in the ", which probably helped the flow, but I wasn't planning on inserting the the ABS inside the cast iron because I don't think that is the proper way to connect the two types of pipes. What do I do in this situation? Do I just connect the large ABS to the CI with the Fercon connector as planned and not worry about the little lip that sits inside the ", which probably helped the flow, but I wasn't planning on inserting the teh ABS inside the cast iron because I don't think that is the proper way to connect the two types of pipes. What do I do in this situation? Do I just connect the large ABS to the CI with the Fercon connector as planned and not worry about the little lip that sits inside the " at the point it enters the main stack?
