A Blockage in the Main Building Drain
The building drain carries wastewater from several plumbing fixtures toward the sewer lateral.
If this shared piping becomes obstructed, more than one fixture may be affected.
For example, using a washing machine may cause wastewater to appear in a nearby shower because both fixtures connect to the same restricted drain.
This pattern suggests a shared drainage problem, although an inspection is needed to identify the actual location.


