Hello good people, I have recently installed a rainwater catchment system on a barn where I am establishing an orchard, small vineyard and berries amongst other deciduous trees for ornament. To date about 3,000 litres are collected for summer use. I noticed that after a hard rain the water is about the color of weak black tea. The roof is about one hundred years old and rusting, though serviceable, it needs to be replaced when the weather warms. After researching a bit I gather terne roofs are not the most sought after for rain collection due to zinc and possibly lead solder leaching. There is no solder on the roof or flashing where lead solder may have been used. My question then is: Since this water will be used to water trees and vines should I be concerned about using it until another (polycarbonate) roof is installed? I dread to think about emptying these vessels and starting over bone dry. I have friends using aged humanure on their fruit trees so I can't imagine this would pose a larger threat than something of that nature. Please let me know if anyone has insight or concerns about this. Thanks, Owl
Lead at high levels is toxic to plants and humans. Your venerable roof probably is composed of steel coated with 20% tin, 80% lead. As you describe it as 'rusting', I surmise that it has not been painted recently: daresay that this condition augments chemical runoff, possibly including a whopping iron content. (This may be the cause of the water's dark color.) Advise you get the water analyzed to see exactly what is in it, and what amounts thereof. Until you possess this knowledge, further advise you to avoid giving this water to any plants bearing fruit intended for consumption.
