What is a common sign of an overtopped septic tank?

The correct answer highlights surface ponding of wastewater and sewage odors as a common sign of an overtopped septic tank. When a septic tank is overtopped, it means that the liquid level inside the tank has exceeded its capacity and starts to flow out of the tank, leading to the accumulation of wastewater on the surface of the ground. This standing wastewater not only poses health risks but also emits strong odors due to the breakdown of organic matter and the anaerobic processes occurring within the tank. Therefore, surface ponding accompanied by sewage odors serves as a clear indicator that the septic system is not functioning properly and requires immediate attention to prevent further contamination and system failure.

In contrast, while algae growth may occur in standing water, it is not a definitive sign of an overtopped septic tank but rather a more general indication of stagnation. Increased plant growth around the tank could occur for various reasons, not necessarily linked to a malfunctioning system. Likewise, unusual sounds from the tank might indicate other types of issues, but they are not as immediate or definitive as the visual evidence and odors associated with surface ponding. Thus, the presence of wastewater on the surface is the most critical sign to recognize in cases of overtopped septic tanks.