"Tony Hwang" wrote in message
newsIZEi.145183$rX4.118238@pd7urf2no...
Bill wrote:


It might not have anything to do with tap/softened water. That
"rainwater" acually contains fertilizer (nitrogen) from the birds and
bugs, as well as whatever minerals leach from your roof.
Hmmm,
Minerals from Cedar shake? Birds, bugs, squirrels, yes.

Probably more so than asphalt shingles. Whatever fallout that gets on your
roof is gonna sit there on the nice damp wood shingles with plenty of time
for the acidity of the rain to help dissolve it. With asphalt, the more
fallout probably washes off the roof in larger particles, and sits in the
bottom of the holding barrel.