I live in a place where we have a lot or chemical plants for processing oil and what not. I set out a large bucket to catch rain water. When I told my brother the bucket was for catching rain water which is mineral free he told me I was wrong and the water is not totally pure like distilled water. He said acid rain would hurt my plants. (He has no CP or gardening experience at all) I set my S. Purpurea and VFT outside and I don't want them to die from the rain water it may receive. Because it rains alot where I live. Should I actually be worried? Is it really going to kill my plant?