I was trying to get a RASP to use as a primary and keep the fass as a backup. Dropped the idea since they are not readily available. I started a thread asking for user opinions on Glacier's version, got no replies.
Went to plan "B". .
Set up a stock pump back by the tank with its own pickup tube as a backup unit, that can be switched over to (should be able to switch over without getting hands dirty). Game over.