I have the same issue and I’m in Palm Coast Florida. Here’s what I found out. I’m considering this. Elastomeric paints are specialty roof coatings specifically for rainwater harvesting. While the material isn't cheap and multiple coats are often required, this could be something to consider, especially for rooftops that aren't otherwise safe to collect from. The National Sanitation Foundation (NSF) provides a list of approved roof coatings for potable rainwater catchment systems.
*All water collected for potable use (e.g. human consumption) must be treated to meet drinking water standards.
