How often do yall sanitize your fresh water tank?

My city water only smells like chlorine once a year during a big flush.
I believe they mostly use chloramine that does not dissipate out of the water.
Remember when you could leave water out for a few days or week to fill a fish tank? Not this stuff. Will kill a hearty goldfish in eight hours after leaving the water out to dissipate chlorine for a week. Just ask my DD. :(