Tried everything, treatments, caustic soda. All professional advisers came to the same conclusion after analyzing this 60 year-old system: Drain field is full and simply will not take anymore water. I had to go to sewer at 30k since excavation and replacement not allowed in L.A. I installed this unit and, after excellent support conversations, expected to see substantial results in about 6 weeks. WELL, IN 5 DAYS MY STUBBORN CESSPOOL DROPPED 20 FEET! No odors and septic level dropped immediately and significantly as well since water there now had someplace to go. ADVICE: Don't excavate! Aero-Stream it! This darn thing in unreal!