I thought of you-all this weekend. I was backpacking in the Sierra and had a little "accident". I've read here about the cross-contamination issue when using a water filter. And this one was a doozie.
I stopped by a nice little stream which was obviously the headquarters for mosquito breeding for all of California (at least). It was also clear they had all just been released from an over-eaters anonymous therapy session, and weren't about to lose any time making up for their lost meals.
Anyway, I used my Miniworks EX to fill my 3L MSR bladder. I had the filter screwed onto the bladder using the conveniently-sized mouth on the bladder. Anyone who has used a Miniworks EX realizes filling a vessel this size, particularly while bathing in hungry mosquitoes, takes a while.
Just as I finished, I lifted the bladder + filter up ... and was about to unscrew the filter. Then ........ SPLASH!!! the bladder gratuitously detached itself from the filter and want splashing into the stream.
I wasn't about to risk using it at that point. Undoubtedly some of the "clean" water was displaced in the fall and replaced by untreated water. I emptied out the bladder in disgust and packed it away.
Fortunately I wasn't counting on that as my only water storage...
So today I splashed around lots of dish washing detergent in the bladder and ran it through the tube for a while before vigorously rinsing the whole thing. Hopefully all the little giardiasis critters and all their friends are gone...