[permaculture] Roofing materials and water collection

Lawrence F. London, Jr. venaurafarm at bellsouth.net
Sat May 14 00:31:42 EDT 2011


On 5/13/2011 11:39 PM, Stephen Sherman wrote:
> Thanks, appreciate the experience. Reinforces what I had heard elsewhere
> about the longevity of the painted roofing.
>
> Question still remains (in my mind at least) is it safe to drink the
> water which comes off this painted roofing?  Would you do it on a
> regular basis?

There's the difference. I do not know what chemicals may diffuse from 
painted roofing into rainwater which may have a low pH. With a 
galvanized metal roof you are dealing with the galvanizing chemicals 
which may include zinc which is toxic and may diffuse into acid 
rainwater. As for fasteners it would be important not to use leadhead 
nails to attach the roofing; this goes without saying. Maybe the painted 
roofing would be safer. What about bird doo and rotted vegetation, dust 
particles of all sorts that get mixed with rainwater?
Purchase one panel each of the 5V galvanized and one of the painted - 
mount them outside and collect water that runs off them - then have it 
tested. Also, get MSDS's (Material Safety Data Sheet) for each product 
and read what chemicals are in the paint and what the galvanizing agents 
are then do extensive Google searches for more info on potential 
toxicity from these roofing materials that might affect collected 
rainwater used for human consumption - maybe OK for washing but not food 
prep or drinking - maybe some filtering required.
question put to Google like:
"toxicity problems with rainwater collected off metal roofing"

Tried that phrase and got:

Information on Zinc Oxide in Construction - Zinc Metal Roofing Systems
The run-off water can contain zinc ions. Since zinc is an element 
essential for life and most organisms ... For instance, rainwater 
collected from VM ZINC roofs, can be used without any known problems for 
watering plants. ... Actually there are many types of heavy metals some 
that are toxic and some that are not. ...
www.metal-roofing-zinc.com/zinc_roofing_basics.htm - Cached - Similar

and:

http://www.homesteadingtoday.com/archive/index.php/t-376478.html

Key reply:
"I wouldn't drink rainwater off a roof unless it had been sterilized by 
some means, boiling or chlorine or such. Bird poop can carry some nasty 
parasites and pathogens. You can do it, and get away with it, but it is 
a gamble."


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