Sanitizing FWT Frequency

[LTRVing]

Been RVing for about 2 years, spending winters south and a number of other trips during the warmer seasons. We've got the process of setting up, tearing down all set. Generally, we do a good sanitization of the FWT and pipes on our long trip south and then after returning the rig will sit for 2-3 months before we get going again. Water systems are drained and blown out during that hiatus.

Our daughter and husband just bought a TT to join in the fun. As I explained the process of sanitizing the FWT, he inquired if he had to sanitize on each trip, with up to a few weeks to a month or more between them? Being an engineer, he thought the contact time for a bleach solution is minutes, not hours, siting government health department information of a 1:200 dilution (1/2oz to 1 Gallon ratio) with a contact time of 5 minutes.
So, with the being said, what is the recommended frequency of sanitizing the FWT's with sporadic use?

Thanks for insight and info.

[SidecarFlip]

That will depend on usage and how long the water in the FW tank sits.

My opinion is, a little bleach in the tank don't hurt anything while it sits. City water usually has chlorine in it anyway. Some municipalities more, some less.

[270S]

City chlorination is in a closed system (no outside air). I drain and refill FWT with new chlorine if sitting for 1-2 months regardless if I am about to use it or not. The tank(s) have pathetic overfill vent(s) and the Chlorine can "evaporate/dissipate". Aside from time and a few cents, it is harmless to redo FWT chlorination every 1-2 months and certainly before you leave on a trip. Don't forget to drain and "rinse" before you start a trip.