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TOPIC: Product Selection

painted metal roof for rainwater harvesting

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I have been told that galvalum is OK for rain water collection. They say that nothing leaches from the metal into the water. I am wondering if there is any painted roofing material that can make this claim. I am going to harvest rain water for potable usage. I would REALLY like to use a painted metal roof so that I can get the best emissivity from my roof. But I don't know, and can't find anyone who can tell me, if their painted metal roofing material will leach any chemicals from the paint into the water as the material ages. Do you know of any? Or am I just going to have to use galvalum? thanks.
tim kamrath

2/18/2013
I know that some individual manufacturers and metal suppliers have studies done in this area. I would suggest checking direct with companies like Englert. ATAS, and Drexel. I believe that you will find results with PVDF-painted metal similar or superior to bare galvalume.
Todd Miller
Isaiah Industries, Inc.

2/19/2013
Thanks for the question. According to NSF (www.nsf.org), filtration is a typical part of rainwater harvesting systems that produce potable water. Impurities can enter the water from the environment (acid rain), from the catchment area (leaching out) or from debris. Our typical recommnedation is that the water be tested periodically to ensure the filtration is effective at producing potable water. Regards, David Stermer
David Stermer

2/19/2013

Generally speaking, are all (or most) metal roofing panels manufactured using powder coating method of painting to be able to offer a 30 to 40 paint warranty?
roger perry
30 to 40 year paint

12/17/2018

There are generally three types of painted products available. In the shingles and tiles, there is also the option of stone-coated panels. The three types of painted products are:

1) Usually just on vertical seam panels, there is is the option of a clear acrylic coating on top of AZ55 Galvalume. This coating protects the metal during fabrication, transit, and installation. It washes away after about 5 - 7 years.
2) Various colored coatings from polyester resin paints. These are the lesser expensive of color coated products and you will find a variety of warranties.
3) PVDF finishes. Sold under the trade names of Kynar and Hylar, these coatings offer the most meaningful fade and chalk warranties. Again, you will find different warranties from different manufacturers.
Todd Miller
Isaiah Industries, Inc.

12/17/2018

I should add, these coatings are typically wet-applied while the metal is still in coil form. There are not many powder coat options on metal roofing as that is a less efficient way to coat the metal.
Todd Miller
Isaiah Industries, Inc.

12/17/2018

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