Cisterns eh.....Well how big is it, where does it get the water from, and where is it stored.
The thing about ones which use rainwater is that birds can tend to make the water harmful...get my drift. There are water treatment systems ...but those are only for treating the water mineral issues...not potability.
Talk to your local water company, or treatment center and get good info for your area. Things change as far as climates and geographic areas. Oceans, power plants, fire prone areas, lots of rain....a little rain....migrating geese.
Lots of issues. Good luck.