Metal Roofs for Water harvesting

Guest User
I design systems for roof water harvesting in the Southwestern USA. I favor metal roofs and would like to have some information to use in convincing clients. First, is there data that shows runoff coeficients of metal vs brai vs foam vs tar and gravel. Engineers using the rational method and favor an over estimation to be conservative. In Roof Water Harvesting, it is necessary to favor an under estimation of runoff to not overestimate supply from the roof. So accurate RC's are very useful, but very difficult to find. Any help would be appreciated. Second, metal roofs are my preferred surface to harvest drinking water. Is there a list of roofing materials or paints that conform to NSF standard 61? Thank you for any suggestions
Allan Reid
Dura-Loc Roofing Systems, Inc.
Interesting subject. We have had our systems tested as they are used extensively in the Carribbean to harvest water. The problem we have found is that in North America there are so many pollutants in the air and people want to hold us leagally responsible. As such we quit handing out the test data. Any bare Galvanized metal will give off zinc in the rain which is its secret to protecting the substrate. I am not familiar with the NSF standard 61 and I would suggest you contact the National Coil Coaters Association to ask them. I can say that along with our granular coating we use the two top paint systems recommended for metal roofing and both of them tested fine. Hope this helps.
Guest User
A friend that lives in Austin, Texas, loaned me an Austin newspaper with an article about a family that built a successful rain water collection system. The home owner is a MD. They have a metal roof on their home and one other large building. They live out from Austin and drilled for water, but did not find it. With their rain water collection system they never run out of water. They have a large family, swimming pool and fruit orchard. Their metal roof is the painted type. They had their water tested and found no problems with it. They add nothing to it, either. Austin has an average rainfall of 32 inches. I remember scanning the newspaper article, so it's on one of our PCs. If and when I find it, I'll get this information to you. The article is large with all the details and very good pictures of the full system. The owner has given talks on how to build these systems. Sounds like you already build these collection systems, but need more information. Good Luck
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