2 questions,, routes and water

Since you say water tanks I wonder if you are asking about your waste water tanks also. As others have said, use bleach in the fresh water tank.

There is no reason to sanitize your black and grey tanks. Just flush them out then put a couple of gallons of water in them so they never dry out.

I also can't answer #1 but I will echo what was said about your second question. Your fresh tanks should be sanitized once each year and that is best done at the start of the season. Water tanks will grow mold, etc. and you don't want to get you and your family sick. Bleach is easiest to use and fast. There are commercially sold tank sanitizer chemicals but why spend money when a half cup of bleach added to water does the same job. Flush with fresh water first, add water and the correct amount of bleach, let sit for four hours (or more) and drain. Flush again with fresh water and you are good to go.

Rickybobby, just in case you hadn't checked back, you are getting route responses to your other post on it.

x2 on Bobbo's response here.

I can't answer question 1, but the answer to question 2 is the water system should be disinfected with bleach if it has been sitting unused for an extended period. Once disinfected, then flush with regular water and just keep using regular water thereafter.

My personal rule is to disinfect if the water system hasn't been used in 3 months.