Occasional sewer backup in basement. Camera showed belly in sewer line in piping from 11 feet in front of house to edge of street. They are also saying there is an offset in pipe under concrete near stack in basement around 10 inches deep. Would the offset be causing the backup or the belly in the front yard. They want to jackhammer up the basement floor to raise up the offset , but my husband does not think this offset is causing the backup. I need another opinion please. Our sewer district has already checked & they are not liable. The line has already been snaked several times & water jetted to clean it.

I am glad you did video inspection. That way you have visual reference as to what is going on with your sewer.

Sewer pipe should have no offsets. Any offset will inhibit sewage flow and may be cause of sewer back ups. Same goes with "belly" in the pipe.

Sewer flows by gravity - from your house to the City sewer. The slope of sewer pipe is subtle, about 1/8" per foot for 4" pipe. If there is a section of pipe with "belly" in it, solids in sewage will accumulate in the "belly" and eventually will cause back up.

Usually, if you have to snake your sewer 2 times a year, there is a problem that should be dealt with. If you were my customer, I would suggest sewer pipe replacement

Hope that helps

Milo

I have to agree with Milo, if you are going to remove these obstructions you may as well pay now to eliminate the root cause of your problem permanently, or else it will fill up again and cause a problem... AGAIN.

Thank you so much for your reply. In the estimate I have (I am trying to help my mother, so I was not there when the plumbers came) they say they want to raise elevation to remove the offset & put back new pvc pipe to pvc stack and repair the concrete, One concern I have is there is no mention of the belly under the front yard. Do you think the elevation of this area will fix the entire problem?

It's very likely that the belly will be eliminated with new piping (depending on where it actually is), but you don't have to assume, presume, or hope. You just ask the contractor your question.