“The First Need also uses an iodine-impregnated filter to remove viruses…”

Hey, you’re in luck Oregon Mouse. First Need uses no iodine!. One of the only filter purifiers (true purifier) that doesn’t use iodine.

“…Manufactured in the USA from the finest raw materials, our water purifiers are ecologically and environmentally compatible; they purify naturally without adding chlorine, iodine or other pesticides to the water you drink and use in your foods and beverages. General Ecology's "Structured MatrixTM" technology is independently certified to USEPA Purification Standards against all three classes of waterborne disease organisms - parasitic cysts, bacteria, and viruses - instantly, without pre/post treatment, without wasting water and without electricity. Outstandingly effective, they also remove chemical and aesthetic contaminants, …”

Lori, you’re right, the ‘blue dye’ test doesn’t check for chemical filtering. It just checks to see if the filter is cracked from droppage or freezing. This is the only filter that can do that easy test. If you see blue dye (or tannins for that matter), then don’t trust the filter! Again, that’s not true for any other filter.

“The directions instruct you that in some cases you should add iodine to the water - which says that is is not infallible.”

The First Need instructions don’t say that. In fact, before or after First Need, no chemicals are needed. You might have got that from the Katadyn Filter instructions.

And yes, it is heavy (relatively speaking). So if I’m hiking anywhere near farmland, I would use the First Need. It “removes dirt, unpleasant tastes and chemicals such as pesticides and herbicides” But I’m glad I’m not backpacking in the midwest right now.
And yes it has a shorter life span. Even though it advertises 150 gallons, in the Midwest I only got ~40 gallons before it dropped to 1L/min. I save those cartridges for gravity filtering for home emergencies.

-Barry
-The Mountains were made for Tevas