From: kanon11@gmail.com   
      
   Ok, I think I figured it out.    
      
   1. In biogas digesters where an upside down floating drum is used, the output   
   level will be close to the level inside the tank.   
      
   2. In digesters where the methane is under pressure, the pressure will push   
   the effluent upwards to some extent. I'm sure this is where know-how comes in   
   to determine just how much. Also note that the input pipe must be long enough   
   so that this pressure    
   doesn't push the manure out of it as well.   
      
   3. When new manure is put in, this will raise the level inside the tank which   
   can push the effluent out the output pipe if its height is correct as in #1   
   and #2 above.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)