My home is from the early 1900's and I have a large main drain that is cast iron. The drains that run to that main one are the kitchen sink, the basement shower, upstairs shower, laundry and upstairs bathroom. The picture is of the grease trap drain that the kitchen sink runs to. Now I moved in 5 years ago and within a year this thing burped up sewage goop as shown 2x so I called in Cleardrain. They jetwashed thru it and he got the camera down to the main street exit underground. Now last week, we had a stinky burp 2x again so I called in Cleardrain again. He said my water drains from the sink down past that trap shown and heads from there to the main drain. The problem this time though was he could not get his camera through the pipe at about 22 feet in and showed me there is corrosion from that drain shown to the big cast iron main drain. He kept blasting water and we got a little further but he couldn't reach the big empty like last time. That was the lovely smelly mess I got to clean up when he left. My question and concern now is what should I do from here. Thank GOD the only thing that causes the burps is from the kitchen sink and not the laundry or upstairs bathroom which gets used a lot. He wasn't 100% sure that its cast iron but he said more than likely. I don't have thousands to do foundation/pipe repair here. I'm finding out cleaners can also be harmful for corrosion so before I go dumping anything down there I'd like some advice. I'm afraid this cleaning isn't going to last another 5 years before we have a nasty smelly burp and mess again. What do you recommend I do with this?