A hydration system is an apparatus used in
recreation
Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for enjoyment, amusement, or pleasur ...
and other sustained
outdoor activities
Outdoor recreation or outdoor activity refers to recreation done outside, most commonly in natural settings. The activities that encompass outdoor recreation vary depending on the physical environment they are being carried out in. These activiti ...
. It is intended to help its user carry
liquid
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
, 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
consumer
A consumer is a person or a group who intends to order, or uses purchased goods, products, or services primarily for personal, social, family, household and similar needs, who is not directly related to entrepreneurial or business activities. T ...
s were first sold to
cyclist
Cycling, also, when on a two-wheeled bicycle, called bicycling or biking, is the use of cycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as "cyclists", "bicyclists", or "bikers". Apart from two ...
s, 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
Western Asia, West Asia, or Southwest Asia, is the westernmost subregion of the larger geographical region of Asia, as defined by some academics, UN bodies and other institutions. It is almost entirely a part of the Middle East, and includes Anat ...
.
In practice, such a system is almost always a commercially manufactured unit that features at least
* a flexible bladder of one or a few
liter
The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: â„“) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). ...
s' (
quart
The quart (symbol: qt) is an English unit of volume equal to a quarter gallon. Three kinds of quarts are currently used: the liquid quart and dry quart of the US customary system and the of the British imperial system. All are roughly equ ...
s') 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.
History
The plastic bladders from
box wine were repurposed as an inexpensive way to store water when hiking in Australia in the late 1960s but were prone to breakage and leakage. 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
''Tunnel in the Sky'' is a juvenile science fiction novel by American writer Robert A. Heinlein, published in 1955 by Scribner's as one of the Heinlein juveniles. The story describes a group of students sent on a survival test to an uninhabited ...
'', where the main character has "a belt canteen of flexible synthetic divided into half-liter 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:
* The largest
dimension
In physics and mathematics, the dimension of a Space (mathematics), mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any Point (geometry), point within it. Thus, a Line (geometry), lin ...
is the
vertical
Vertical is a geometric term of location which may refer to:
* Vertical direction, the direction aligned with the direction of the force of gravity, up or down
* Vertical (angles), a pair of angles opposite each other, formed by two intersecting s ...
one, taking advantage of the long vertical dimension of the human
torso
The torso or trunk is an anatomical term for the central part, or the core, of the body of many animals (including humans), from which the head, neck, limbs, tail and other appendages extend. The tetrapod torso — including that of a human â ...
.
* The hose joins the bladder very near the bottom of the bladder, to maximize the amount of accessible liquid.
* The bladder's change in
volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). Th ...
as it is gradually emptied is reflected in the decrease of its smallest dimension (
thickness
Thickness may refer to:
* Thickness (graph theory)
* Thickness (geology), the distance across a layer of rock
* Thickness (meteorology), the difference in height between two atmospheric pressure levels
* Thickness planer a woodworking machine
...
); this lets the vertical and side-to-side dimensions stay fixed, thereby limiting the shifting of it and any items next to it, and minimizes the flexing of the bladder walls.
Packaging
Typical commercial hydration systems are available with three fundamental approaches:
* A "bare bladder", intended to be carried in a matching pocket of a "hydration-system compatible"
backpack
A backpack—also called knapsack, schoolbag, rucksack, rucksac, pack, sackpack, booksack, bookbag or backsack—is, in its simplest frameless form, a fabric sack carried on one's back and secured with two straps that go over the shoulders ...
. (Such a pack will usually also feature a hole through the pack, near the upper anchoring point of the pack's shoulder straps, sized for the hose and bite valve to pass through it, and often covered by a flap that prevents rain entering the pack through it.)
* As part of an integrated design incorporating both a backpack and the hydration system (usually sold together as a
hydration pack
A hydration pack or drink bag is a type of hydration system built as a backpack or waistpack containing a reservoir or "bladder" commonly made of rubber or flexible plastic. The reservoir contains a capped mouth for filling with liquid and a h ...
), usually with at least a few pockets-worth of storage space for other items. (Such a combination is likely to have a channel inside one or both shoulder straps, for the hose to pass through, preventing the hose from tangling with other gear or the environment, and ameliorating the annoyance of the liquid warming up while waiting in the hose to be drunk next, or the problem of it
freezing
Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid o ...
.)
* A basic hydration system in a protective fabric shell, so that the bladder is unlikely to be damaged by other gear that it shares the interior of an ordinary pack with. (The
CamelBak
CamelBak is an American outdoor equipment company based in Petaluma, California, best known for its hydration products, such as hydration packs and water bottles. CamelBak is also a supplier of protective gear and other products to the U.S. mil ...
brand products of this kind are trademarked as "The Unbottle", for instance, and each looks a lot like a very small pack, with a hand-carrying strap at the top and four
D-rings that could facilitate attaching it to the outside of a pack. However, they completely lack shoulder or waist straps.)
Accessories
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 (for instance by clipping to the hose, or looping around it and snapping to themselves to close the loop) 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
MSR may refer to:
Science and technology
* Macrophage scavenger receptor, a receptor found in macrophages
* Magnetic stripe reader, a device used to read magnetic stripe cards such as credit cards
* M–sigma relation, in astrophysics
* Mars samp ...
, 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 (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
A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...
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.
* Depending on the size of the opening for filling the bladder, it may be convenient to include, in hot weather,
ice cubes
An ice cube is a small piece of ice, which is typically rectangular as viewed from above and trapezoidal as viewed from the side. Ice cubes are products of mechanical refrigeration and are usually produced to cool beverages. They may be produc ...
or crushed ice when filling it. In theory too much ice means running out of liquid water while the bladder still has ice occupying space that could have been filled by more water (so it helps to take account of how
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
and
humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.
Humidity depe ...
affect the balance between consumption rate and melting rate), but it helps that most people's tendency seems to be to put in less ice than would last through the hike.
* The use of liquids that provide
calories
The calorie is a unit of energy. For historical reasons, two main definitions of "calorie" are in wide use. The large calorie, food calorie, or kilogram calorie was originally defined as the amount of heat needed to raise the temperature of o ...
(usually in combination with
flavoring
A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of the gusta ...
and perhaps
rehydration salts) increases the cleaning burden by nourishing bacteria, and if the user neglects to empty and rinse the bladder, judging the cleanliness of the bladder at a later date involves more effort than with containers that are more
transparent
Transparency, transparence or transparent most often refer to:
* Transparency (optics), the physical property of allowing the transmission of light through a material
They may also refer to:
Literal uses
* Transparency (photography), a still, ...
and in some cases more accessible. Some users carry plain water, with or without ice, in a bladder, but drink something else from
Nalgene
Nalgene is a brand of plastic products developed originally for laboratory use, including such items as jars, bottles, test tubes, and Petri dishes, that were shatterproof and lighter than glass. The properties of plastic products make them suit ...
-style bottles during rests.
* On trips over a day, or in especially hot conditions, need for more water than is carried may require
purification of local water.
** Attention to mechanical compatibility of a filtration system with the bladder, or with a Nalgene-style bottle that may be carried to fill the bladder, can be worthwhile.
** Use of chemical purification systems raises issues both of staining of the bladder and the possibility of weakening its material. Besides the
aesthetic
Aesthetics, or esthetics, is a branch of philosophy that deals with the nature of beauty and taste, as well as the philosophy of art (its own area of philosophy that comes out of aesthetics). It examines aesthetic values, often expressed th ...
discomfort of drinking from a perfectly
sterile but "dirty looking" bladder, staining can also interfere with judging later the cleanliness of a bladder.
* Another way to ensure the bladder does not start a breakout of microbes is to let out as much water as possible from it, and freeze it as soon as possible. This technique makes use of the property that microbes cannot propagate under freezing conditions.
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 3/16 inch (5 mm) of the air) warms or cools relatively rapidly toward the
ambient temperature
Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...
, 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
The word oral may refer to:
Relating to the mouth
* Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid
**Oral administration of medicines
** Oral examination (also known as an oral exam or or ...
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.
See also
*
Hydration (disambiguation) Hydration may refer to:
* Hydrate, a substance that contains water
* Hydration enthalpy, energy released through hydrating a substance
* Hydration reaction, a chemical addition reaction where a hydroxyl group and proton are added to a compound
* H ...
*
Hydrational fluid
Oral rehydration therapy (ORT) is a type of fluid replacement used to prevent and treat dehydration, especially due to diarrhea. It involves drinking water with modest amounts of sugar and salts, specifically sodium and potassium. Oral rehydrati ...
References
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Camping equipment
Military personal equipment
Drinkware