This method is easier because you won't spend anything at all but then it's hard to practice this because our air these days is also not safe.
With the amount of particulate matters dominating our airspace these days, I won't consider. However, rain water is still considered the purest form of water and it passes through that space before reaching the earth. So, maybe there is nothing to worry about here. Brilliant suggestion, though.
Rain water is safe but that’s if you get it directly from the sky and not your roof top. That method of water purification is a form of water chlorination which is a very good way of purifying water so for those people living in open and well vegetated areas, they can practice that and get a great result.
Thank you so much for your comment 🥰