Guess That's Why They're the Expert

Sewer backup: one of the least
disgusting photos on the Web.

Roto-Rooter identifies 3 Signs a Sewer Backup is Coming: [bold added]

1. A foul stench coming from drains.
2. Slow draining bathtubs or laundry lines.
3. If the use of other fixtures associated with your main line lead to water backup in places such as toilets or showers.

Foul stenches, slow-draining washing machines, and toilet backups mean that a sewer backup may be coming. Brilliant. That's why they're the professionals.