I actualy splurged and used Captain Phab Purge Tank Cleanser this year to try it.
I used to use bleach every spring then spend the day flushing the bleach tast out .whith the Captian Phab I simply put it in and filled up the tanks. ran the water to fill the lines and hot water heater , toped up the tank and let it sit for a day (I actualy did two days) then drain and flush once. this was the first year that I had neither bleach or antifreezed flavord water on my first trip. I was a little hesident due to the 25 buck price tag, but it will do two seasons on my 5th and camper so thats realy not bad.
Steve