Let me revive this thread. 2 tbsp/5 gal = 7.8 mL/L is a perfectly acceptable concentration of bleach to do the killing, provided you also add the same volume of white vinegar to bring the pH down so that you produce hypochlorous acid which is the sanitizing agent (don't add it directly to the bleach unless you want to die young). At least, that's what Charlie Talley, maker of Star San, says. He also notes that the required contact time for sanitizing at this concentration is only 30 seconds. He says this is no-rinse and that it's impossible to taste at this level.
He says the reason for adding the vinegar is because a lot of bleach makers make it from table salt, which results in lye being introduced into the chlorine at some point which pushes the pH up. He says buying the cheapest store-brand bleach, making sure it is a very clear yellow-green color and smells like chlorine is your best bet.
Hear
this podcast from basic brewing radio to hear the interview.