Lori is correct. Bleach is not considered effective against crypto and giardia. Nor do municipal systems use it. Older systems use cholrine (in gas form, I think) and as time goes on, municipalities are moving to chlorine dioxide which is effective against the above. A prime reason for the change was the breakouts of giardia from treated municipal water of sytems using the older chorine treatments. The incidence of giardia breakouts has been sigificantly reduced with the chlorine dioxide treatments. Many (most?) of the upgraded systems have also added UV treatment as a final 'dose' for the water.

When it comes to filters the main thing is size. What is the size of the threat and does the filter filter out buggies of that size? Specs from the manufacturers I've looked at give that information.

FB