Some time again, my neighbour told me that rain water is better for the plants than tap water. Is this true? Both tap and rain water come from open sourse such as rivers or paddocks. Tap water has been treated and cleaned. But I guess rain water is pure H20 since heavier elements could not evaoprate. Is that way rain water is better for plants? Does rain water contain more mixtures of nitrogen compounds mixed in it? If so does that help as plants need the nitrogen but cannot absorb it directly from the air.