How do you carry enough H20 in the heat while backpacking?

We're doing the challenge and we recently did Cucamonga and stayed overnight at the summit. We began with 21 liters of water between the three of us and refilled at the spring in both directions, total consumed was about 26 liters for the trip. Baldy has no spring on the way up the Devil's Backbone and wondering how everyone deals with the 100 degree weather, when it comes to staying properly hydrated? My friend carries 9 liters and I normally carry 13 liters for Lynne and myself. I'm considering adding another 6 liter reservoir, for a total of 19 liters, but that's 43 lbs. of water weight. Thanks, John