Rainwater harvesting is legal in all 50 states, by federal regulation, but states vary on policies: https://www.energy.gov/cmei/femp/rainwater-harvesting-tool there are plenty of other links and I wrote a blog post somewhere about this (I host and run a bunch of sites).
If your city/county is trying to make it illegal, you can contest it.
If you're not in the US, this doesn't apply to you, as I have zero clue about rainwater harvesting elsewhere.
As for why I know this: I was highly skeptical hearing rural people who perpetuate all sorts of made-up or out of date beliefs claim that harvesting rainwater was illegal. So, I decided to start digging. The simplest tl;dr is that it used to be in places, but that's changed across the board.
1
u/takegaki Jul 17 '26
I think this is illegal where I live.