Bladders and Bottles
Water can be carried in bladders that fit inside the backpack as well as bottles in side pockets. Some people adapt a front harness so water bottles can be held on the front of the body. The Aarn backpack has pockets on the chest to hold water bottles.
You will have many choices and the time to find out is during the training. Check out the options at your nearest outdoor store.
There are pros and cons of any system for carrying water and some people will only buy local bottled water on a Camino. Yet, there are always plenty of opportunities to fill or top up with safe drinking water.
Bladders in the backpack are very popular and can be filled in the morning before starting the days walk. One concern I have is that if there are a lot of places to top up it is difficult to do with a bladder inside the backpack so the tendency is to start with a days supply which might be 2-3 litres weighing 2-3 kgs. That might be a lot of unnecessary weight when only 1-1.5 L is needed.
If stopping for coffee or snacks then water is usually freely available to supplement your own supply.
On some Caminos, including the Via De La Plata, there are long stretches of over 30 km with no water available along the way. Having a 3 L capacity is a must particularly in hot weather.
I have used both and have a slight preference for bottles in the side pockets of my backpack as I can monitor my intake, easy to top up and depending on the backpack design are usually easily reached.
Find out what works for you based on the quantity you are likely to need daily at the time of the year you will be walking.
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