Hugh,
I just recently returned from a trip to New Zealand, where I stayed in private homes in small towns on North Island. I was surprised to learn that these small towns don’t have public water systems; every home in the town has its own rain catchment system. The system catches unfiltered rain water from the roof of the home, draining it into large above-ground tanks in the back yards. (It doesn’t ever freeze on North Island.) Most of the homeowners I talked to had no idea how the system worked, but I did find one fellow who said the water is pumped into the house with an electric pump that runs the water through a .2 micron filter. Apparently, these systems perform for years without any maintenance at all. One home had “stuff” growing in the rain gutters that fed the tank. I was at first concerned about drinking the water, thinking that maybe the locals had developed resistance to any “thing” that might be in the water, but I did eventually drink the water with no ill effects. It seemed like a pretty simple, reliable system for supplying water to a household. – R.K.
Hugh Replies: I noticed that my MSR water filter has a .2 micron filter, and I have used it in some very questionable back country waters. While this level will protect from most things, some viruses can be .02 microns, though they are rare in water systems. Most viruses are in the .25 to .4 micron range, which can be filtered out by these filters. If there is a question of contamination, boiling remains one of the most effective methods along with UV.