No blockage was found in my sewer lines.

Also a settling or sagging foundation can causes sewer lines to collapse or break causing blockages.

I also install cleanouts if I'm routing piping underground in the event of a blockage.  

He cleared the blockage and told me there was 'a belly in the lateral line'.

Building in a downtown area typically involves privacy fencing the entire site, permits for road blockages, fights with neighbors over port-a-potties, and difficulty with noise ordinances. 

if the vent starts deteriorating this can happen with partial blockages.

We've had calls for HVAC problems, plumbing blockages/leaks, electrical issues, (not light bulbs!) 

At least then, when it has to pump, water will get out rather than come back due to sewer line blockages.

@Brie Schmidt...lol....maybe in the wall..when it's backing up in the tub, there is a blockage somewhere...The camera is worth the extra cost when it's not obvious...what about the pressure?

It's been about 20 months since the work was done, and there has been zero problems with any sort of blockages or sewage back-ups, for a basement bathroom.