Yes many years ago it was illegal to have your own rain water tank if you lived in the city limits, we had a farm and always had rain water tanks I just remember how sweet it used to taste free of all that chlorine and fluoride.Now with all the water shortage problems its becoming obvious how ridiculous the ban on rain water tanks is, and a lot more municipalities are allowing rainwater tanks or at the very least those storage tanks that have a pump usually it can only be used for the laundry and the toilet, but not showers funny because its the shower that wastes the most water. Some also allow grey water systems where by all the waste water from the shower, sink, and laundry are collected and can be used to water the yard. The argument the city councils use is that bacteria in rain water can cause health issues because its not treated.
There's some folks around my neighborhood that have rain barrels attached to a gutter system. And they use it to irrigate their gardening projects
I don't see anything wrong with it.
Also when I was younger I spent alot of time in the Bahamas in the less touristy areas. And that was their only source of fresh water. Every house or business had a big cement cistern attached to it.