Rain water harvesting from metal roofs

Jim Ryan
Rain Water Harvesting
2/27/2005
Dear experts, There has been a proliferation of different coatings and paints factory applied to metal roofs, is there a guide to which of these is safe (hopefully tested) for producing potable water when used as part of a rain harvesting systems? Obviously anti-fungicidal coatings are likely to be un-safe to use, what about the others? And while we're at it, what is the best metal roof to use for rain harvesting, ie the roof material which will not react with and pollute the water, and which maintains a slippery clean surface which quickly sheds accumulated dirt when the rains first strike it. Thank you! Jim
Todd Miller
Classic Products, Inc.
2/27/2005
Many quality paint systems are often applied after the metal has been treated with a chromium-containing pre-treatment solution. This solution is rinsed and then covered with paint but, still, no manufacturer is going to suggest the use of their panels for drinking water collection if therr is a chance that chromium pre-treat was used on the metal. I would suggest bringing this subject up with individual manufacturers but, given today's liability environment, I doubt any manufacturer of any prodouct is going to say "Yeah, go ahead and drink water froom my roof."
Guest User
3/5/2005
Todd, How do you square your answer to my question with the answer to a similar question from your expert Allan Reid who says.... "To the best of my knowledge, all residential roof coatings are safe to collect the rain water. In fact you will have greater risks with the rain itself. I would say that you should specify a PVDF or SMP paint system or a granular coated roof, as they will provide the best weather resistance". Also, I know in countries like Auistralia and New Zealand, it is standard for metal roofing companies to specify which roofing systems and coatings are approved for potable water collection. Could you at least give me the meanings of the PVDF and SMP paint systems? Thank you, Jim
Todd Miller
Classic Products, Inc.
3/5/2005
Sometimes, two seemingly opposing answers may very well both be correct.
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