If you live in a condo and have a backup caused by the main sewer line in the building the HOA emergency # should be called. 
If you do not have the HOA emergency phone # then call us please at (619) 220-4840 Ext 6 any time and we will provide it for you .

The following are indications that the main line is backed up.

1:In a single family property , several fixtures in your residence will back up simultaneously.
2.In a multi family property , you and your neighbor(s) have a back up simultaneously.
3: If using a toilet or other fixture you notice water coming out of the bathtub or shower drain.

The following video may help too.