This here is a sewage backup in a commercial building. What causes sewage back-up?
1. Tree roots: tree roots can cause a couple of problems for your sewer lines - they can grow into the pipes and cause holes and blockages or they may wrap around your sewer line and crush it.
2.Broken or collapsed pipe: Although plastic sewer lines have now become the norm, older homes were built using cast iron and clay piping that can break down over time and create sewer problems.
3. Clog: your main sewer line can become clogged, which can cause sewage backups in your home.