What you need more than a water capacity is a water strategy. Having a water strategy means learning how to hike in reasonable comfort through areas that are hot with long dry sections. This means knowing when to hike, when to rest, when to start in the morning, when to stop at night, how to cook, when to cook, what to eat and when, how to dry camp, etc.
You'll be starting early ahead of the crowd. Which is good for getting water from the various caches. However, if you've not already developed a water strategy, it'll be harder to join up someone else and learn.
If you can, I'd try to get back to the Kickoff and attend the water seminar. At the least you'll want to bookmark the water report on the web. If you're carrying a smart phone, you'll want to update it to the latest report every time you hit town.
There are plenty of opportunities to add or remove water capacity at the various stores you'll pass. Developing a functioning water strategy is not so simple.