I avoid iodine for health reasons so I use the mp1 tabs with a non-chemical 20oz water bottle filter when space permits carrying the bottle. That takes the wait time from 4 hrs to 15min (though I give it 30min to be safe). When space does not permit (like with my normal EDC) I have to wait the 4 hours. However in a situation where dehydration within 4 hours is even a remote possibility, this is a non-issue because I would simply use the MP1 tabs and be drinking in 15-30 minutes. If you read Dougs extensive write-up on this you'll find that this is not such a bad plan. I'll take the slim chance of diarrhea over dehydration and certain death any day if given only those two options. <img src="/images/graemlins/wink.gif" alt="" />