PSW,
I add about a 1/4 to 1/2 gallon of bleach into our 41 gallon fresh water tank and then fill with fresh water. It is a very strong mixture. I then run it through the system including all faucets, the hot water tank, & accumulator, then top off the fresh tank again and let sit in the entire system for an hour or two, not longer because I heard the bleach is hard on the waste tank valves and some faucet seals, basically anything rubber. After a complete drain and refill twice & such, we are good for the season. The water smells like a swimming pool for not more than a week. We'll use it for cooking and drinking after the smell is greatly reduced by boiling for a while, but generally avoid drinking cold only for the peace of mind.
I sterilize the fresh water plumbing at the beginning of the season and only the waste tanks at the end of the season to avoid sewer gas in our garage. I don't know if what I do is good or bad but it's worked well for us for 8 years so far.