Hi Linley
As previously posted check your fill up hose also. Buy a food grade hose from bunnings as these don't tranfer the plasic taste to your tank. I haven't used bi carb before, I usually 1/3 fill my tank and put some milton tablets in it (kills bacteria also) then drive around the block a few times. I leave it in for a couple of hour then rinse. This has worked well for us so far.
Regards
Jas