Hydration, hydration, hydration! The most important part of any physical activity that humans undertake, staying properly hydrated is not only important for your health but has a direct effect on your abilities to undertake your trip. Especially as we enter the warmer seasons, making sure you're getting enough water becomes more and more important as temperatures rise. If you're going on a camping trip you likely have the room and weight capacity for larger amounts of water, or even access to running water. However, for backpacking trips carrying multiple gallons of water is just not realistic. Water isn't just heavy, it takes up a lot of space, which becomes the largest luxury on a backpacking trip.
For the inexperienced backpackers out there, I wanted to discuss how you can properly stay hydrated on a multi-day backpacking trip. First and foremost, you should ALWAYS bring as much water as you can make room for and physically carry. Don't strain yourself carrying more water than you comfortably can, as the extra weight will cause you to work harder, dehydrating you faster. Whether you choose to use hydration packs or carry bottled water out with you, that will be your starting point. The containers used to hold your water can be refilled and reused throughout your trip, but where you refill that water from needs to be taken into consideration. Although a fresh stream might appear as otherwise clean water, there is always a chance of harmful microbes and bacteria, which is especially true in any stagnant water pools. To be clear, if survival is a concern, having water is better than not having it. However, outside of absolute survival necessity, you should be taking steps to purify your water before consumption.
This is one of the easiest and oldest methods of water purification in human history. We all need to eat, so it's very likely we'll have a way to bring water to a boil. Whether you do this with a camp stove or over the fire, you can heat up the water in a cooking pot, or even a disposable plastic water bottle. If you don't have any actual cooking pots, filling a water bottle to the brim allows it to be boiled inside the plastic, without destroying the plastic. Take caution, as this can only be done a handful of times before the water inside may be compromised, but this has been proven to work in a pinch. Otherwise, boiling the water will kill the bacteria and microbes within, giving you clean drinking water. Great for making tea, or letting it cool to room temperature to refill your canteens and packs. If you pulled water from a wild source, make sure to strain the water through a cloth or towel to catch any solid sediment prior to boiling. Even if the water is cleaned, you don't want to ingest the sand and soil that is floating in there.
Iodine or chlorine water purification tablets have been available for a long time in most outdoor supply stores. These tablets react with water, releasing the chemicals to kill off the bacteria and microbes that might be nesting in the water. By collecting water from a source in a container, one or more tablets would be used, depending on the volume of water, to purify what was collected. There are a multitude of manufacturers out there that will purify the water up to 99%, making it likely cleaner than even the tap water you may have at home. While this is great, there is a bit of caution to these tablets. Firstly, you must ensure the tablet is entirely dissolved. The tablets are not toxic if properly used, but should never be ingested directly. Secondly, there is of course a slight chemical taste, but this is very minor and for many, unnoticeable. Keeping a few of these in your pack is always a great idea, as you can purify larger volumes of water, even if it's not your primary method. The benefit that these tablets employ is that they work just by dropping them in water, requiring nothing else to function.
Much like a water filter you have at home, there are many devices to pump water through a series of filters. Some devices operate with a battery, using an electric pump, while others work simply with squeezing or suction, such as the LifeStraw. A product like the LifeStraw makes sense for backpacking, as it's very lightweight and small, making it easy to pack. While electric pumps won't find their ways into most backpackers kits, there are smaller devices that are functional for backpackers - however they work slowly. If you're setting up camp for the night near a water source, those pumps can be useful in those cases. If none of those sources are available to you, there is a simply purification method that can be done with the objects around you. Using a plastic zip top bag, stack a layer of sand on the bottom, adding a stack of small pebbles on top of the sand. The top layer could be a piece of cloth - a towel or piece of a shirt. Add a small puncture to the bottom of the bag, and pour your water into the bag. The water should trickle through the layers, giving you water that is relatively sediment free. This will NOT remove any bacteria or microbes, so it's recommended to boil this water afterwards, regardless. What this will do is remove the large sediments, giving you clear, but not entirely clean, water.
To summarize, there is no single right or wrong way to restock your water supplies on the trail. This comes down to individual preferences, and especially what you are able to carry with you. It's always recommended to have backups to purify water in the field, as relying on the water sources you bring solely can lead to issues of dehydration. Be sure to plan ahead for how many days your trip should take, carrying enough water for at least an extra 48 hours if possible. If not, extra supplies for purification to ensure you can restock your supply is a must.