[GlennWest]

Mine was where the water hose flush was mounted on side of tank near the top. The flange had cracked, I assumed from over tightening, and seal was compromised. Quite a job to get to to fix. At first it just stunk when tank was full. We were very "green" about a rv and just assumed it needed emptying. Odor would go away after emptying. It got worse and I slide those panels back and got a big surprise. We've tried about everything to get rid of odor. I also replaced my commode last year and everything looked good and sealed properly on top. Planning on removing bottom, wiping everything down with Lysol and replace insulation.