[permaculture] Roofing materials and water collection

Jason Gerhardt jasongerhardt at gmail.com
Thu May 26 23:51:03 EDT 2011

Glad this topic came up again. I am finishing up teaching a PDC in Arizona
where water has been a main thread of conversation. At Brad Lancaster's home
in Tucson he said he currently drinks water off his galvalum roof without
problem. He has yet to test his water quality however. After talking with
many people on this subject I've determined essentially that Darren
Doherty's comments on this thread are what holds true. Each individual will
likely adapt to their specific water quality or lack thereof. Brad wouldn't
let others drink his water since he believed he was adapted to it, but did
not want to risk offering it to others.

I also hear that ARCSA (American Rainwater Catchment Systems Assoc.) has a
ton of information on this issue. According to an attendee of a recent ARCSA
conference, researchers in Australia have found that rainwater is basically
very pure regardless of the surface it runs off of, even asphalt shingles.
>From what I understand, the biofilm inside the tank (or the bacterial film
that clings to the sides of the cistern) are a key element in keeping the
water clean. When this biofilm is cleaned away the water quality actually
goes down.

Brad Lancaster suggested if one were worried about water quality from roof
runoff for drinking water that it could simply be run through a home
purifier.  He suggested Potter's for Peace, which makes a simple colloidal
silver filter for unpressurized systems.

For what it's worth,

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