Mt Whitney Zone
Under the best case scenario, the Mt. Whitney trails will open after July 2. I have a day use permit for July 3, so it's certainly possible that I'll be one of the first people this year to be going up the Main Trail beyond Lone Pine Lake.

If that really does become the case, would the water sources above Lone Pine Lake be safe to drink without filtering? The odds of finding a WAG bag in or near, say, Trail Camp Pond would be extremely slim, but would pollution from non-human sources be an issue? I mean, I wouldn't want to be drinking unfiltered water that has marmot poop in it!
If you want to be totally safe, use a filter pump or iodine tablets. If you feel lucky, drink the water untreated. The only way to know for sure would be to send samples to a lab. Those who have contracted giardia says it is very unpleasant. We always used iodine tablets because they weigh nothing to carry. Follow up in 30 minutes with a vitamin C tablet to remove the iodine taste.
Following Bob Rockwell's example, I have always drunk the water in the Whitney Zone unfiltered. I was up there last spring, drank from the North Fork, and various places along Lone Pine creek. We camped 3 nights at Trail Camp. The pond still had several feet of snow cover, and the only water available was snow melt running across granite slabs just below the pond. I repeatedly refilled my water supplies from that spot, and never experienced any trouble during or after the trip. When the pond is melted out, I prefer to go to the stream flowing into the pond and fill up at that point. By now, the water may be flowing across the switchbacks above Trail Camp, about switchback #25. I would drink that water any time, as well.

Of course your preferences matter the most, so it is up to you what you do.
I use a Katadyn BeFree filter. For $40 and 2oz, you don't have to even think about it.

It's small enough to put in a pocket empty and bust out at each lake or spring whenever you get thirsty. My water-carry weight for most sierra hikes or runs is 0.
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