Thanks for the info Ed! I am currently using 2.25" with an inner tuber of 1.5" both 8" long, the unit could handle anything up 3" for the outter tube and the inner around 2" or so if you have some scrap laying around! :)
Short story, my pool is a salt-system pool. The pool water contains about 5000ppm of NaCl and the system passes current through a cell to produce Cl. After about 5 years the cell has failed, I am trying to fab up my own replacement. For first attempt I used 316L stainless, this lasted about 5-6...