New To Site

[Ismellelephant]

I was hoping for some suggestions as I am puzzled now.
Gushing Toilet
The video is a basement toilet, on the same vertical soil pipe there is a first floor and second floor toilet. When flushing the second floor toilet, water gushes out of the basement toilet. I am on a septic system and have no backup issues at all.
Searching everything points to a negative pressure issue, like a blockage in the soil pipe. What I have done so far is removed second floor toilet and using a camera I was able to see a clear path from there to the top of the soil pipe on the roof(see pic). Also, I was able to look down the pipe to the basement clean out(I put a light in) and it also appears clear(see pic).
I am having the septic tank pumped, it has been a while, but I can't think of a reason the septic tank would be involved in the gushing basement toilet issue.
I have also tried leaving the clean out open to affect air flow, and the issues remains the same.
Thanks for any input to get rid of my Bidet.

 

[Tuttles Revenge]

There is something blocking the drain below where the upstairs toilet dumps into the main and the septic.

 

[Sponsor]

 

[Ismellelephant]

Thanks for the responses. If there was a block of some sort wouldn't I be seeing a backup? Everything disappears as normal. I was also able to run 23 feet of snake from the cleanout to the direction of the septic tank. After the tank is pumped I plan on using a jetter down the soil pipe and to the septic tank. If still an issue I'll call a plumber.

 

[Tuttles Revenge]

Perhaps there is a belly in the pipe. But seeing an explosion from your toilet like that when the upstairs is flushed tells me that the water is forcing air to go past the trap of the toilet.. explosively.. that can't happen unless there is something blocking the drain and the venting for the toilet.. otherwise the air that is being pushed by the flushing water would just go down the drain or up the vent.

have a camera scope the drain.

 

[Ismellelephant]

Perhaps there is a belly in the pipe. But seeing an explosion from your toilet like that when the upstairs is flushed tells me that the water is forcing air to go past the trap of the toilet.. explosively.. that can't happen unless there is something blocking the drain and the venting for the toilet.. otherwise the air that is being pushed by the flushing water would just go down the drain or up the vent.

have a camera scope the drain.

Thanks for the response.
Yes that is exactly what is happening, air being push through the toilet. I know there is about 15 feet of old original Orangeburg pipe still remaining under a cement patio. The remainder of the run to the tank is PVC. I was able to snake 23 feet through the Orangeburg to the PVC section. What is puzzling is you would think a blockage would cause a backup, but I haven't got that issue.
I'll keep plugging away.

 

[Onokai]

(Orangeburg pipe still remaining under a cement patio. The remainder of the run to the tank is PVC. I was able to snake 23 feet through the Orangeburg to the PVC section. )
That stuff completely fails at some point. My guess is you have passed that point