I've purchased a 35 gal ace roto mold tank for holding RO water while I mix it. I want to use the bulkhead to install a pump in-line that will be 'T'ed off and valved with one leading back into the RO tank (for mixing) and the other to a hose (for filling the sump). 1) What is the best pump to use for mixing purposes? Are some brands better for being externally mounted? Should I spring for a ceramic shaft? The sump will be 36" from the tank with no head so I don't need an overly powerful pump. I'd prefer something with an enclosed housing for the motor as there's bound to be drips. 2) I believe its a 1" bulkhead , if I replace the bulk head should I go with a narrower diameter or is it just as well to reduce down the existing bulkhead once I have my pump picked out? 3) any 'gotchas' associated with externally plumbed pumps? I'm looking forward to automating this part of the process. Thanks!