usually just using the boicide and new filters will do the trick. I would not pull or drain the tank until I tried that. Personally I have never drained a tank for bacteria, the biocide will kill it and render it able to run out through the filter and burn off.

Good luck!

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.