What kind of roofing materials are compatible with a rainwater catchment system?

Think smooth. We joke about the merits of glass roofs (stone-throwers aside), but when we stop laughing and get serious, we’d have to say the best roofs for rainwater collection are metal. If your existing roof isn’t metal, don’t despair. Unless it’s flat and covered with tar and gravel (whoever invented this roof should be tarred and gravel-ed) or one of the old asbestos nightmares, nearly any roof can serve as a collection surface. It’s not the particles, like those that might be washed off composition shingles, that present the biggest obstacle; those can easily be filtered out. Rather, it’s the chemicals, like those used to treat wood shingles, that cause problems in water collected for potable use. Fortunately, activated carbon filters in combination with ultraviolet light can remove nearly everything except radio-active particles and, most inconveniently, lead. Answer excerpted from Richard Heinichen's Rainwater Collection for the Mechanically Challenged, available on rainwater. ...  more