We buy a small bottle of beach every spring , pour it in and let it sit for a day. I think that is the trick to get the stink out. Then next day we flush the tank out with all the faucets open, both hot and cold, with a hose in the fill opening going about half blast with the water so that the tank does not run dry. If you use the pink stuff it get all of that out. It does get rid of the stink and cleans the lines.
Yes don't use this water to drink. We always have a case of bottled water on hand for drinking.