I have my own private well for all my water needs, that water is filtered for sediment, treated with UV, softened, and for drinking pre-softened water passes through a Reverse Osmosis filter... thing is an RO filter makes 3-4 gallons of gray water for each gallon of filtered water, that gray water is piped to my lawn where it flows via gravity to water a few shrubs. Were I collecting rain water for drinking I would definitely RO filter it, untreated rain water is poluted. Anyone drinking collected rain water is drinking worse quality water than the gray water from my RO filter. No one drinks so much water in a day that they can't afford to produce some as gray water, certainly less than a few toilet flushes. RO filters are very inexpensive, costs far less than element filters and works a thousand fold better than any other filtration system. Considering the price of an RO filter and the cost of water (I still need to pay for my well water in electric and maintainence) each gallon of RO filtered water costs five cents... and also saves more than it costs in not having to buy bottled water... bottled water is just ordinary tap water, albeit from someone elses tap... buying bottled water is paying for plastic bottles and transportation, the water is pretty much free... those plastic bottles are huge polutants.