Water and sewage from toilets, drains, and sinks backing up into the home’s plumbing. Bathtubs, showers, and sinks drain very slowly. Gurgling sounds in the plumbing system. Standing water or damp spots near or over the septic tank or drain field Sewage odors around the septic tank or drain field. Bright green, spongy lush grass over the septic tank or drain field, even during dry weather. Straight pipe discharging untreated wastewater to the ground surface Algae blooms in nearby lakes or water bodies. High levels of nitrates or coliform bacteria in surface waters or drinking water wells.