Backflow in drain plumbing: what it is, why it happens, and what to do.
In the drain context, backflow means wastewater reversing direction and coming back up through a drain. This happens when the drain system downstream is blocked and cannot pass waste forward, so it comes back through the lowest available drain — often a floor drain or basement shower.
Main line blockage is the most common cause.
When the main sewer lateral blocks, wastewater has nowhere to go. The path of least resistance is back up through the lowest drain. Stop using water immediately and call for emergency drain service. Call Sunburst Environmental at 678-799-4389.