There are multiple warning signs that your main sewer line is backing up. Be mindful with the problem before the sewer clogs entirely and damages the house. (1) Slow draining bathtubs & sinks. (2) A ripple sound when you flush the toilet (3) water comes up in the basement floor drain or a first-floor bathtub/shower when the toilet is flushed (4) There is a constant need to plunge toilets. (5) sewer smell coming from drains.