If there is any nick or deformity in your oring then it will not seal. You would need a new one. The same can be said of the stainless. If it is dented and air can get by the o-ring then it will not seal. Inspect with a magnifier if you can not see imperfections. Remember that the dip tube seals 2 places. The ID of the post and between the dip tube and dip tube housing. O-rings can not have any nicks or debris that keeps them from sealing. The wrong size o-rings do not work either and they must be food grade.
Fermentor 1: Bill's House Ale II, Fermentor 2: German Helles, Fermentor 3: Bill's Schworzbier (Black Bier)
Tap 1: Bill's House Ale II, Tap 2: German Hefewizen, Tap 3: Nut Brown Ale
Future Brews: Stone IPA Clone, Blonde Ale, Budvar Clone, Newcastle Clone
New toy: Blichmann 27 gallon fermentor
“If you find yourself in a hole, the first thing to do is stop digging”
“Good judgment comes from experience, and a lotta that comes from bad judgment”