Unimogbert - thank you for you excellent well thought out comments.

I'm looking for anything that would be better than nothing.

I think with meters someone could learn to safely handle the cleaning of a boiler and the proper storage & disposal of filters (even emulating compliance with regulatory standards).

I have two water source scenarios in-mind (at this point it is only academic):

First scenario: stationary in a small house in small town with city water --- whose source is an underground aquifer; a closed system. Potential backup sources would include ditches in or about town and roof water.

Second scenario: (to be avoided if at all possible) is having to get water from bayous, abandoned rice irrigation canals or gullies.

As to the second scenario, I've been looking around for "packaged" non-electric water distillers - hardly any out there but here is one: http://www.waterwise.com/productcart/pc/1600.asp

If it is a long term event, I think the biggest issue would be having an adequate supply of fuel so as to run the boiler for the duration.

I haven't seen anyone yet suggest the possibility of filtering the contaminated water first, for instance with Katadyn's Ceradyn (with 0.2 micron elements) and then (also) distilling it. This, of course, would only be an option at a stationary location.