On Wed, 24 May 2006 20:16:46 +0100, Dave Fawthrop
wrote:

Rain water is by definition very soft, and will dissolve lead fast.

Indeed, hence the importance of properly patinating any freshly cleaned
lead roofwork. Bare lead will pinhole if left untreated (actually it
probably won't now - back in smoky '50s cities it was a different
matter).

Once patinated though, it's a different story - the surface is no longer
bare metallic lead. A lead storage cistern is an issue, but rain simply
passing over a lead roof isn't going to collect any measurable lead
content.