Here is a rough picture of how my bathroom is plumbed now.
The issue I am having is the toilet is hard to flush. It is slow to flush, and when it does it will blow air back up the toilet. If I take a shower it will slowly blow air up through the toilet. And when the washing machine drains, it will blow a lot of air up through the toilet. Pictured is one of two branches that go out to the main sewer line. The other branch work and drains fine.
One night the entire bathroom wouldn't drain and started backing up into the other branch. Had a plumber come out and run a snake up under the house from an outside cleanout. Cleared the clog and everything ran great. Even the toilet i was having issues with. But 2 days later the toilet started backing up and blowing air again. Yesterday I pulled the toilet and ran 50 ft of snake down into it, reinstalled the toilet and it worked great, flushed normally, didn't blow any air when running the washing machine. But that only lasted a day until it started again.
All this started after we had a flood and I had the contractor move the washing machine drain into the wall. Before it was a 2" pipe running up from the floor thru the ceiling and venting in a whirly bird in the attic. The washer drained into a wye pipe into this drain. When he moved the drain into the wall he never vented it. So on this whole branch the only drain it the 2in at the end of the line.
Ideas? Is there still a partial blockage somewhere in there or do I need to go extreme and install a vent line between the toilet and the main branch?