After some experimentation I think I may have figured this out. Pure water may drop from adventurer packs, rubble, bookshelves. The drop rate seems related to the difficulty level. So the fastest technique seems to be farming the Bonebite Hideout on elite level. I tried my capped wiz and my capped cleric, both work fine. I kind of prefer my cleric because soundburst, inflict serious mass, and even bladebarrier with quicken let me clear out the kobalds pretty quick. There is a shrine right there if you need it. I use a second account to refresh the instance quickly. I am getting plenty of prayer beads and other needed items for the rituals.
I still wonder, is the drop rate higher on the elusive Alchemy Tables?
<strike>I posted about this recently but didn't get a satisfactory answer, so I'll try again.
I am looking for Vials of Pure Water, used in the Alchemical Armor Eldritch Ritual for +1 dodge. I believe pure water only drops from bookshelves and alchemy tables. Unless it has a really low drop rate elsewhere. I believe alchemy tables have the best drop rate but I'm not sure. I have checked most of the remaining harbor quests and can't find any alchemy tables. (Not in Baudry's, Ringleader or WW, which were responses I got earlier.)
This is not an Amber Vial, which drops all over. That is a different collectable.
I can't go to Korthos Island to look for Pure Water, because I was born in Stormreach several weeks ago. Or did they fix that? I haven't heard anything.
So, where can I farm Vials of Pure Water? I'm parched!</strike>
...