Signs of Failure Your septic system may be failing if:  A foul rotten-egg smell is noticed  Your tank overflows  The soil around the tank is soggy  Yours drains are slow or overflow  There is a gurgling sound when sinks are drained  A foul smelling liquid leaches out  There is dark green grass around your tank and/or bed  There is a wet, black oozy liquid around the trenches Your septic system may fail for any of the following reasons: –Your leaching bed is not coping –Your septic tank is full, get it pumped out.