I got a private message from a new member, thought I'd share my answers here.
...my husband and I will hike Mt. Whitney on July 11, 2019 (camp at Trail Camp) and summit on July 12th. We are in our late 50's and I'm worried about snow and ice. Should we take crampons and an ice axe? Please can you give me some help on what we can expect and any pointers to help us make this hike go smoothly.
We took a class at REI this week on learning how to use a compass and read a map in case we get lost. Will the trail be marked so we know the direction?
Also, how much water should we be carrying and drinking for this hike?
And is it a good idea to leave our tent and sleeping bags at Trail Camp when we summit on Friday morning? We live in Iowa so we are not used to the elevation.
P.S. We have hiked 12 - 14'ers in Colorado in the last 4 years.
Snow and ice: Take the switchbacks. I posted several pictures of them from other hikers in the Current Conditions thread, and the toughest place is the cables--people have had to climb over them and hang on the outside to get past a short steep spot where the snow is too steep. ...but maybe in a week that will have melted so you can stay inside the cables.
The only other places on the switchbacks have several sections where you need to traverse along a snow slope. When the snow is soft, you can probably just stomp through it. If it's icy, crampons would be good.
Also, between Mirror Lake and Trail Camp, there is a snow covered traverse that is giving people trouble. Crampons are definitely helpful there.
You don't need an ice axe unless you want to climb or descend the chute, which I think is a bad idea. You need crampons to climb it, and need to know how to use the ice axe as a brake when glissading. ...or you could down-climb it, but then you should just take the switchbacks.
Trail: The trail will be pretty easy to follow when you are there. Be sure you have a map. In what snow remains, just follow the main tracks. Do not descend after dark--in these conditions, people sometimes miss the left turn (to the north) down to Mirror Lake, and get into dangerous areas around the waterfall above Outpost Camp.
Water: I dip and drink, have never had any bad results. But you can filter or treat if you want--it's a personal decision. If you dip at trail Camp, get water from the inlet of the pond there. So when I hike, I only carry 8 oz or less until Trail Camp, and make sure I drink 8-12 ounces at every water crossing. If you're filtering, you will probably want to carry more and filter at fewer spots. Make sure you are drinking copious amounts--you often don't feel thirsty, but that makes the AMS worse.
When you leave Trail Camp, take 3 liters/quarts. Finish one by the time you reach Trail Crest. The second will get you to the summit, the third for the way down. You could get by with less if you keep scooping clean snow into your container as you go, and it will then melt so you can drink it. An old timer I know would stash his third full container at Trail Crest, and pick it up for the way down.
Altitude, AMS (Acute Mountain Sickness): When you hiked 14ers in CO, did you stay at altitude several days before hiking? I know Denver is at 5k, so several days there would definitely help. When you go to Mt Whitney, I hope you plan to stay several nights at Whitney Portal, or better, spend a night at Horseshoe Meadows (10k) and a second there, or at Whitney Portal. By doing that, your body is better prepared to haul all that gear up 4K elevation in one day, and camp at Trail Camp at 12k elevation. If your CO climbs were really quick and you had no trouble, then maybe you will be ok on Whitney. Just beware.
Leaving gear: People always leave their gear at Trail Camp. Just leave tent open--marmots might chew a hole to get in otherwise. ALL food/snacks left there MUST be in a bear-proof container, not for the bears, but for the squirrels and marmots. They chew into everything else.