thanks for the links to rainwater collecting and solar stills, av. those are very helpful.
i hate to ask the same question again, but elgeco/jim, what material is your roofing made of? because i think different roofs can be more/less harmful depending on what they're made of. mine is asphalt shingles, which is why i am more concerned about chemicals leaching. but if you two have asphalt shingles too, and no problems, maybe i will worry less about it.