It's a great way to get low TDS water to run thru a DI tank. In some areas you can get into trouble for capturing rainwater so make sure there are no restrictions in your area.
I recommend you run the rainwater thru a DI tank for best performance.

This world is all screwed up. You get in trouble for capturing clean water and you get in trouble for discharging dirty water. What a crock of S hit, not good.

It does stink for sure Art. A few years back when the IWCA convention was in Atlanta I was talking to local guys who couldn't capture rainwater or they faced a fine. Here in the Midwest I've never had an issue but many places out west and down south can run into this problem.

I wonder if it was a municipal law. Not trying to argue because I haven't done extensive research -yet, but I've also read that there are in reality no states that have an outright ban on harvesting. Some may require a permit, mostly to assure no ground contamination.
I guess it comes down to doing the footwork for whatever state you live in to be sure.

Dan it was due to the drought there at the time. Unless you had the mineral and water rights to your property you couldn't capture rain water at that time.
Most people don't know that they may own the land their house sits on but anything below that (oil, natural gas, gold, etc) is property of the State or Federal government as is the rain water falling on it unless they have the mineral rights to that property.