Yes, it is.  elete does not contribute to the growth of mold or bacteria so it is fantastic for hydration systems.  To use elete in your hydration system, add 1 capful per 32 oz or 1 liter; 2 capfuls per 2 liter or 70 oz bladder; 3 capfuls per 3 liters or 100 oz bladder.  When you’re done, just clean your pack as you normally would.