I have a 2500-gallon above-ground plastic cistern which is filled with water caught from my composition roof. I was using it to irrigate my mostly-ornamental garden. I replaced most of the ornamentals with a food forest. I've been told that the water isn't safe to use on edible plants
because of the heavy metals in the shingles. It's a 30-year roof which I had installed in 1999 before I discovered permaculture.
I've read about sand filters that are used in the Third World to purify drinking water. They don't seem to be legal for sale in the US. I also heard about a paint that could be used on an asphalt roof to reduce the toxic effects of the heavy
metals in the shingles. Does anybody have experience purifying water caught from a composition roof? If possible, I'd like to use my own water to grow food.
Thanks,
Susan
Seattle
