We're looking to collect rainwater to put into our cistern (currently it's trucked in). I'm sure there are lots of folks on this site who have made their own water filtration systems for such a thing, and I'm looking to learn! From what I understand, the first water to come off the roof is toxic (too much bird poop, I believe), so it's good to divert that water. Then I was thinking we could utilize rain barrels to hold the water initially (we've put in two, and use that water for watering plants or outdoor cleaning projects, but it's not filtered in any way for safe drinking/cooking). I was thinking I might be able to utilize some 5 gal buckets for filtering, by nesting them into each other and drilling holes into the bottoms. The first bucket would have gravel, the second would have sand, and the third would have carbon (contained in netting so it doesn't go out the bottom). Then I could route the water into the cistern. Does that sound safe? Any advice, recommendations would be appreciated.