I was getting a bad odor from my aerobic septic system when the sprinklers would activate. I had the tanks pumped out and verified they were cleaned out completely. After a few days the system filled up and the odor is still there once the sprinklers activate. The last time the tanks were pumped out was 3 years ago so I don't think that is a problem. The aerator pump is humming along like it always does. The middle tank has a gurgling sound that I can only assume is normal since the air is being pumped into this tank. Is this correct or is this my problem? Chlorine tablet routine hasn't changed. Same number of people in house. I think I had this issue before but it was the aerator pump that had gone out. Any ideas?