Greetings, We have a challenge. Our second floor toilet is often not flushing correctly - any thing more than just liquid is a problem. It sounds like a venting issue, but I can't find it. Plunging helps right away, until the next time....

Pouring about 9 gallons of hot soapy water into the vent stack helped, but only for a while, and not completely.

Putting a 23' painters extension down the vent stack struck nothing. Today, I put a 10 meter USB cable camera in, and could not see anything, but it hit something at about 30'.

That sounds like it's close to the basement floor.

The 3.5 story house is about 90 years old. It came with a second floor full bath (which has the problem) and a basement toilet - but I think that was supposed to be a "Pittsburgh Toilet" - i.e., mainly just a way to detect backups. We have City Sewers. About 50 years ago, a 1/2 bath was added on the first floor, tied into the existing waste stack. It has its own vent stack.

About 5 years ago, we had an addition built and started using a second waste stack at the back of the house. It previously only served the kitchen sink. That has had 2 clogs in the 5 years, but none since we became extra careful. It has 30' of pipe under the slab.

The trouble with the 2nd floor toilet started after some clogs in the adjacent sink. The first clog, I could clear with a 1/4" auger, For the second one, I had to get a plumber, who had a slightly heavier auger. I was able to hear the auger in the walls, telling me that the sink drain connects to the main stack on the same floor.

I am wondering if anyone has advice before I give up and call a plumber?

There have been times when the basement toilet was dry (suggesting vent issues), but it is not dry now.

Climbing on the roof is getting harder to schedule, with early winter sunsets.

It occurred to me that a cleanout in the attic might be useful, but there are cleanouts in the basement, one at shoulder level where one of the new connections is, and a few at floor level, on either side of the house. (I don't have any experience with cleeanouts :-)

Thanks for any advice. The next thing that occurs to me is bleach, which has been known to help for sink issues in the past. I bought 3 gallons...

Thanks

Seth