Help with leaking ABS DWV pipe

[willingtotry]

I have ABS DWV pipe in my house to drain the upper floors. A 3" ABS pipe enters the basement and makes several turns before it connects to a 4" ABS pipe to leave the basement to travel to the septic system. The seam where the last 3" pipe connects to the 4" pipe appears to be leaking (enough to fill a bucket in a day or two). I am aware that I can buy plumber's epoxy at the hardware store to slap around such joints. But, is this a permanent or temporary fix? If permanent, does this meet code? How likely is it to work? If it doesn't work, will it screw things up for the "real" repair? (I am not anxious to do anything to the 4" pipe since that leaves the house and would be very difficult to replace.) Are there other repair options than using the epoxy? Should the 3" pipe be replaced? Is this a difficult repair for a professional plumber or can a "rookie" give it a shot? Any help would be appreciated. Thanks!