I'm replacing 4" Cast Iron Sewage plumbing with some ABS. I was able to replace a section of old cast iron with ABS and connect the new ABS pipe into the female gasket on the Cast Iron side. I believe the depth of the rubber gasket was about 2 and 1/4" deep on the inside of the old pipe. I was able to get the ABS to go about 1 and 1/2" to 1 and 3/4" into the cast iron. I'm wondering if that is deep enough. Afterwards I noticed that the cast iron pipes a re about 1/16 narrower than the ABS which explains the really difficult time I had getting to 1 1/2" of connection. I used a lot of soap. I also sanded a slight bit off the edge of the ABS to help it go in. Will that be enough to keep the sewage going downhill? This is under my slab floor so I have to know for sure before I pour the concrete. Do I cut it back out (not able to remove it) sand a lot more off and try again?
Note* it took two men pushing with all our strength on a six foot lever (huge steel pipe) to get the ABS to budge the 1.5 inches.