What's the last reliable place to fill up with water on the way to Whitney summit on the main trail? I understand there's a spring somewhere along the switchbacks? Or should I plan on filling up before that?

How much water do you recommend each person carry from that last fill-up spot, to the summit and back down to the fill-up spot again?

It's near the 23rd switchback. I drink my fill and don't carry any to the summit. I think you'll get a range of responses, though.

The "how much to carry" is a loaded query -- ask 10 people and you will get 20 answers.

The last time that I gave my amount, someone else did the "are you nuts" routine, so I will refrain.

(HI, are you nuts?)

Even if you are a camel -- like HI -- I would still carry some water for First Aid purposes, ie, something in the eye needs to be washed out, a scrape needs to be cleaned, a sudden bum knee turns what should be the 'planned' amount of time up/bsck to refill.... into thirsty hours..hours..hours..

OK I will be the first in the "Are you crazy" category. SB 23 runoff is very reliable, but not carrying water between there and the summit is, uh, effing unreliable advice, no other way to put it. Unless of course you are used to doing 2000 foot climbs and descents over 5 or six miles, at altitude in the driest air you can imagine without thinking of a little sip or two for five or six hours.

Tom, I knew you were a beast, but it didn't realize you were part camel.

Steve,
To answer your question, generally, 3L from Trail Camp to the Summit will suffice. Also take into account electrolyte replacement, which may be another 1/2 to 1 L.

I have always filled up at the inlet to the lake at Trail Camp, not from the lake. I'd rather have a "for sure" source when I'm refilling water and not be looking for a spring that may or may not be running at the exact time I am there. However, that's what works for me. Hike your hike.

The issue with the spring on 23, is that if you are getting the very early start that you probably would benefit from doing, you may be there on the way up when the water flow is frozen.

I've always thought in terms of 3-4 L from Trail Camp, stash one near JMT junction for the descent.

I don't think its a spring on 23 but a surface outflow from the moraine above, which collects a lot of snow, even in low precip years like the past 3. This is not a technical distinction, but a very practical one. As a surface outflow, it is much more prone to daily and seasonal freezing and thawing than a spring. SO sometimes, it may not be flowing in the morning, but if it is not frozen very solid, you may rely on it, coming down, later in the day. It was flowing well, for example, last August 25, in a record low snow year, about noon. It is in fact a main inflow into the Trail Camp pond.

BTW it looks like a spring because it runs under the talus, but not beneath the soil, and so it looks like it is running deeper than it is.

Maybe we've been lucky but the water on the 23rd switchback has been reliable each time I've gone. Forever more we will always fill up on the way to the summit. Learned our lesson one year when our group of seven did not top off and each of us ran out or ran very low and shared/rationed with each other while we were still on the way to the summit. I ended up sharing my water with one member directly from my Camelbak until I ran out too. Hiking behind him I see a glittering bottle of Gatorade in a mesh pocket on his pack and I point out to him "Hey, you have Gatorade!" and he replies, "I know, I just can't reach it." That speaks more of the loss of rational thinking at high altitude, but my real point is that I will always carry plenty of water to the summit and encourage my teammates to fill up too. Someone might really need it.

I always get water near the inlet to the little pond at Trail Camp (this year there were WAG bags on the shore near the trail when I was there a few weeks ago), and I leave TC with 2-3 liters. I regard water on the 23rd switchback as "emergency water" as it's sometimes frozen in the wee hours, even in August, but most always running by the time I return. Once I did use it on the return.

Personally, I wouldn't use the 23rd SB as a primary water source given the proximity of the pond at Trail Camp, as you may lose upwards of an hour backtracking to the pond in the event the water isn't available on SB 23.

There are plenty of rocks to crack the ice.

You may want to take this with a grain of salt as I have only been uo Whitney once, a day hike in June of this year, but I can tell you exactly how much luquid I took in between Trail Camp and the summit and the return, one quart of water plus a 20 ounce bottle of Sobe Green Tea (sweet and minty, I love it). I didn't suffer any ill affects, so I assume this was plenty. I did give a second quart of water I had to another hiker, but I don't think you can count on fellow hikers as a reliable source. I saw several hikers who looked like they were really hating it. I even suggested to a couple of them that they should turn around.

Water quantity is a personal thing, period. All I can tell you have run out taking two liters and 4 liters. It depends on many factors heat, humidity, work load, etc.

The rule of thumb is 16 to 24 oz. per hour activity...I regularly weigh 2 pounds less after a 30 to 40 minute run. Those who advocate a 2 L carry or drink 2 L come off the Trail Camp to Trail round trip dehydrated.

I always take 4 L. I am usually into the 4th liter on the when I retank.

Finally, if you are stuck up there for any reason, don'cha think it would be nice to just tad bit of water?