Backpacks with hydration systems have become very popular since their development, and many types of packs are available with hydration systems that vary by brand. The size of the backpack is the most obvious difference among several models, though features such as pockets, daisy chains, gear loops, waist straps, chest straps, suspension systems, and many other comfort and performance features are available as well. The hydration system can vary as well, and backpacks with hydration may feature bladders with folding tops or screw tops, insulated or non-insulated hoses, and bite valves that operate in different ways according to the manufacturer's designs.
The size of backpacks with hydration systems will vary according to the user's needs. A backpacker, for example, will generally use a much larger backpack with a different design than someone who day hikes or mountain bikes. A backpacker's backpack is likely to be large enough to carry a significant amount of weight in only one to four compartments, while a smaller day pack may only carry a spare jacket and some snacks in one or two compartments. The shoulder and waist straps of a backpacking pack will feature thick pads, while a day pack will feature less padding or no padding at all. Some straps are mesh for better breathability, and since less weight will be carried in the pack, padding that is lacking on the mesh straps will probably not be missed.
The bladder and hose design will vary in backpacks with hydration according to the manufacturer's specifications. The bladder can vary in size, with larger bladders intended for longer trips or activities. The length of the hose will have an impact on routing options, as the hose will often run through a sewn hole in the backpack to make access much easier. Many backpacks with hydration feature an insulated sleeve sewn into the shoulder strap to guide the hose as well as insulate the water inside of it, preventing the fluids from warming up excessively or freezing.
Some backpacks with hydration are designed to be slim and minimalist; they are often able to be worn under jackets or other garments, which can help keep the water from freezing. This is useful for activities such as skiing or snowboarding, during which wearing a backpack outside of the jacket may be uncomfortable or cumbersome. Some athletes prefer a more minimalist design to cut down on weight and bulkiness, which can slow the athlete down during an event.
