Hydration system


A hydration system is an apparatus used in recreation and other sustained outdoor activities. It is intended to help its user carry liquid, to support the physical effort involved in the activity, without the need to use one's hands or take off the pack. Such systems for consumers were first sold to cyclists, and by the 1990s had also found a substantial market among hikers. Familiar commercial models can also be recognized occasionally worn by western military personnel in southwest Asia.
In practice, such a system is almost always a commercially manufactured unit that features at least
Also common are designs that include specific hands-free means to comfortably carry the hydration system.

History

Hydration systems first appeared commercially in the late 1980s or early 1990s, at backpacking stores. They were adopted by US special operations troops in the early 1990s, and became standard issue for all US troops in the later 1990s.
The concept of the hydration system appeared in Robert A. Heinlein's 1955 novel, Tunnel in the Sky, where the main character has "a belt canteen of flexible synthetic divided into half-litre pockets. The weight was taken by shoulder straps and a tube ran up the left suspender, ending in a nipple near his mouth, so that he might drink without taking it off."

Hardware

Bladder designs

The overall geometry of the bladder is nearly universal:
Typical commercial hydration systems are available with three fundamental approaches:
Some manufacturers offer parts for replacement or customization, whether compatible only with their own hydration systems, or usable also with others'.

Plumbing

Shut-off valves

Especially while a hydration system is being carried in a vehicle, there is some danger of the bite valve being squeezed, opening it to leakage or a steady flow; this can be guarded against with an additional valve, usually installed between the bite valve and the hose, that stays open or closed according to the position of a lever.

Elbows

The bite valve may be installed with a right-angle extension between it and the hose, to achieve a preferred positioning and angle of the valve relative to the user's mouth.

Hose anchors

Position and angle may also be adjusted by clips that clip usually to a pack strap and control the hose's path

Insulation

Hose

Plastic foam surrounding the hose can be used to reduce heat transfer between the environment and liquid in the hose: keeping a cold liquid cool longer in summer and slows a liquid freezing in winter.

Bite valve

At least one manufacturer offers a tethered, slip-off, foam cowl that slows freezing of the liquid in the bite valve, and also reduces contamination of the bite valve.

Filters

At least one manufacturer, MSR, offers a in-line ceramic based filter, allowing use of local water supplies for refill. Ceramic filters can be cleaned at home by back flushing with clean water so no replacements are needed.

Between fillings

Scrubbing systems

Sets of cylindrical brushes permit mechanical removal of biofilm that will grow on the surface inside the system.

Drying systems

Means of holding the bladder walls apart to encourage drying between uses are available, such as a plastic frame that collapses to pass through the fill opening, but expands inside the bladder to hold the sides apart even near the corners.

Techniques

Various specialized practices may be applied in using a hydration system.
Two views exist on the practice of blowing air back through the bite valve, to force the liquid out of the hose and back into the bladder.