I will have to look up the sentinal tank sounds like a good story. About the toilet paper filter assembly, you need a long column is my understanding and the chemicals used to manufacture the paper actually add chemical elements to the oil which improve the properties of the oil. So it is not just the filtering properties that are acting on the oil it is the residual chemicals in the manufacture of the media that also have a positive effect on the final product. I have never build one but my friend had and his was about four feet tall (1.22 meters) good luck hope it helps some.