Sanitary sewer backups usually occur in the lowest open drain. A sewage backup is typically caused by a blockage somewhere in the line. If you experience a backup every time you flush or run water down your sink or bathtub drain, then the problem is likely in your main sewer line since all drains rely on the main sewer line to drain properly. However if backups are limited to only one drain then your problem is likely isolated to that drain.
Regular backups may be a symptom of broken or deteriorating sewer lines If you experience backups or blockages regularly even after having the pipes cleaned,then you may have an underlying issue such as tree root intrusion, channelling, crack sletting surrounding soil in, or a misaligned pipe connection. These issues can be detected by getting a sewer video inspection.
If you can smell sewer gas in or around your home or building, this is a tell-tale symptom that there is a crack somewhere in your sewer system. A sanitary sewer should be air tight everywhere with the exception of vent stacks on your roof which allow for the sewage to move downhill. This means that you should never smell sewer odor unless there was a crack or opening in your sanitary sewer lines.
In addition to sewer odor, mold growth may also be a sign of a break in your sewer lines behind your walls. There are molds that only need the humidity level to be higher than 55% to start growing. Considering that, a cracked sewer pipe behind a wall can cause the humidity levels to rise to a point suitable for a mold problem to begin. If you notice mold growth in your home accompanied by sewer odor then you likely have a break in your sewage drain pipes.
A slow drain may be a symptom that a blockage is forming which will eventually lead to a sewage backup. If your toilet, bathtub, or sink is draining slowly even after attempts to clear the line, you may have issues such as tree root intrusion, channelling, or cracks, mentioned above in the beginning stages.
Note: Beware of using chemical drain cleaners to solve a slow drain or blockage. As the chemical sit in the pipe they will eat away at the cast iron and/or PVC.
Spotting an extra green and lush patch of grass in your yard may be due to a sewage leak underground. Since sewage acts as a fertilizer for vegetation, leakage from your main line into the surrounding soil will give the surrounding grass extra nutrients that will result in a lush and extra green appearance.