When I first started backpacking, and before I had a filter, I would often times carry 4 to even 6 Liters of water. Seriously? 12 pounds of water? That doesn't even include the amount of weight added by all the water containers. I digress. I had the realization on the amount of water to carry on a trip to the Big Frog Wilderness in southern TN, northern GA. I had my 1L nalgene and 2L water bladder. I had recently purchased a pump and left the iodine tabs at home. My bladder was running low so I stopped at a stream to fill it up. It was an epiphany of sorts. On trips like this, I have an unlimited water supply, and I don't have to carry that much in my pack! This really helped advance my journey into the ultralight relm. Diving more into the whole hydration process, I've come up with a decent system to help stay hydrated on the trail.
This step is key. When there is a big trip planned it is important to take all of the necessary precautions to be prepared (food, gear, etc..). Add prehydration to that list. In the days before your hike (5-7) drink lots, and lots, of water. Pack an extra liter of water with you to the trailhead and down it before you start; leave that bottle behind. Being hydrated before your hike saves you weight by hydrating your body, and not your pack with unecessary extra water.
Depending on the area of the trip, I never have more than 2L of water at a time. If try to gauge it to where I drink about a pint an hour. If possible, take a lunch or extended break around a water source during the middle of your hike. When you get to a point you need to refill and find a spot to do so, knock out a liter on the spot and fill it up again before you hit the trail.
Know the Area
Do your homework and study the map. It's important that you know where all the big water sources are with respect to your route. Check online for trip reports to see if streams are dried up or for good campsites with nearby water sources.
I can't stress this enough, but if it's possible, pick a campsite by a good water source. That way you have an unlimited supply to cook with and have to drink. During your time at camp, try and knock out 1-2L before you call it a night. That morning, drink an entire liter before you hit the trail.
This is my system and it works very well for me. This way you will never have more than 4 pounds of water weight at a time. Coordination is key with this system. Know the route and know where the water is at all times; that's what makes this an efficient system.