Hydration bladders
The drinking system
A hydration system always consists of a drinking bladder, i.e. a plastic water reservoir, and a hose with a drinking valve. Modern trekking, touring and daypacks regularly have their own compartments or suspension devices on the back inside the pack to integrate the filled hydration bladder into the backpack. The drinking tube is fed through a small opening in the backpack and along the holders on the shoulder strap to the mouth, where it is ready and securely fastened. The drinking valve can be opened by light biting pressure and usually has an additional closure that prevents the water from leaking.
Many advantages in one system
An integrated drinking system convinces with a whole range of advantages. The hydration bladders usually have a capacity of 2 liters or 3 liters. Thus, a hydration system provides a larger amount of water immediately available than a conventional water bottle and can supply you with water even on an extended day trip. The flat shape of the plastic bladder also helps you make the most of the space in your backpack. The plastic bubble contracts when you suck water through the hose, so that the water can not slosh in your backpack. At the same time, the positioning close to your back supports your center of gravity concentration and balance even with heavy load weight.

Other features that distinguish a good drinking system:

the constant and uncomplicated availability of fresh water,
the absolutely tight and leak-free processing,
the use of tasteless, non-toxic and antibacterial plastics
wide openings for easy filling and cleaning and
low dead weight.