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 * a flexible bladder of one or a few liters' (quarts') capacity with some means, usually a screwtop, to fill and then reliably seal it, * a light hose to convey the beverage to the user's mouth, and * a bite valve that starts and stops the flow through the hose with minimal effort. Also common are designs that include specific hands-free means to comfortably carry the 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 a flexible bladder of one or a few liters' (quarts') capacity with some means, usually a screwtop, to fill and then reliably seal it, a light hose to convey the beverage to the user's mouth, and a bite valve that starts and stops the flow through the hose with minimal effort. Also common are designs that include specific hands-free means to comfortably carry the hydration system.

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 (for instance by clipping to the hose, or looping around it and snapping to themselves to close the loop) control the hose's path

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.

Scrubbing systems

Sets of cylindrical brushes (e.g., a large one for the inside of the bladder, and a thin one with a flexible handle long enough to run at least halfway through the hose) 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.

Clearing the hose between drinks

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. Advocates point out that liquid in the hose (where it is all within of the air) warms or cools relatively rapidly toward the ambient temperature, and value the reduction of this when nearly all the liquid is in the bladder. There it is as much as several inches (10 cm) from the bladder surface, and it may be still further insulated by a pack and its other contents. When the air temperature is below freezing if the hose isn't cleared it can rapidly freeze blocking the hose. This often occurs skiing where high wind speed and low temperatures are combined. Detractors believe that blowing into the hose increases the amount of oral bacteria inside the bladder, and requires more frequent scrubbing to keep the flavor and odor of the contents acceptable. Because the hose attaches to the bottom of the bladder, in order to let the last of the liquid into the hose, air that reaches the opening bubbles to the top of the bladder, and is trapped there until the liquid is nearly drained. Each time more air is blown into the bladder than the amount of liquid contained inside the hose, the pressure inside the bladder increases, and the more effort blowing back involves. Therefore, the technique profits from enough attention to develop a sense of when the hose is nearly full of air.

References

Text derived from https://en.wikipedia.org/w/index.php?oldid=1343216432 under CC BY-SA 4.0; modifications have been made.