Leaking 3” toilet waste

[bweinzveg]

I have a two story house with a wall hung toilet upstairs, with cast iron pipe in the wall on the 1st. floor to reduce noise from flushing. This setup has been in use since 1981 with no problems. We had company this past fall and they were using the upstairs toilet and we noticed a wet spot on the carpet on the 1st. floor where the 3” cast iron is in the wall. I thought it was the gasket where the wall hung toilet is attached to the Zurn support in the wall. I took the toilet off the wall and decided to make sure that it wasn’t the pipe in the wall before I reinstalled the toilet. Well it turns out that the pipe is leaking I think where the cast iron is joined with the ABS pipe. I wonder if the connector was not tightened enough and just started leaking. I know that there would be two connectors, 1 at the bottom and 1 at the top. I ran a hose down the pipe about halfway and it leaked. Telling me that the lower coupling is the one leaking. I was going to get hold of an inspection camera to locate the joint to know where it occurs in the wall to access it and tighten the coupling screws. Any advice would be greatly appreciated