In recreation

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 pleasure and are considered to be "fun"...

 and other sustained outdoor activities, a hydration system is an apparatus

Apparatus

Apparatus may refer to:*Technical term for body of the Soviet and post-Soviet governments *Machine*Equipment*Critical apparatus, the critical and primary source material that accompanies an edition of a text-See also:*Fire apparatus...

 intended to help its user in drinking enough liquid

Liquid

Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

 to support the physical effort involved in the activity. Such systems for consumer

Consumer

Consumer is a broad label for any individuals or households that use goods generated within the economy. The concept of a consumer occurs in different contexts, so that the usage and significance of the term may vary.-Economics and marketing:...

s were first sold to cyclists, but by the 1990s also had found a substantial market among hikers. Familiar commercial models can also occasionally be recognized being worn by Western military personnel in southwest Asia

Southwest Asia

Western Asia, West Asia, Southwest Asia or Southwestern Asia are terms that describe the westernmost portion of Asia. The terms are partly coterminous with the Middle East, which describes a geographical position in relation to Western Europe rather than its location within Asia...

.

In practice, such a system is almost always a commercially manufactured unit featuring at least

• a flexible bladder, of one or a few liter
  Litér
  - External links :*...
  
  s' (quart
  Quart
  The quart is a unit of volume equal to a quarter of a gallon, two pints, or four cups. Since gallons of various sizes have historically been in use, quarts of various sizes have also existed; see gallon for further discussion. Three of these kinds of quarts remain in current use, all approximately...
  
  s') capacity, with a means (usually a screwtop) of filling and then reliably sealing it,
• a light hose to convey the beverage to the user's mouth, and
• a bite valve for starting and stopping the flow through the hose with minimum effort.

Designs that also include specific hands-free means for comfortably carrying are common.

Bladder designs

The overall geometry of the bladder is nearly universal:

• The largest dimension
  Dimension
  In physics and mathematics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify any point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...
  
   is the vertical
  Vertical direction
  In astronomy, geography, geometry and related sciences and contexts, a direction passing by a given point is said to be vertical if it is locally aligned with the gradient of the gravity field, i.e., with the direction of the gravitational force at that point...
  
   one, taking advantage of the long vertical dimension of the human torso
  Torso
  Trunk or torso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. The trunk includes the thorax and abdomen.-Major organs:...
  
  .
• 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
  Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....
  
   as it is gradually emptied is reflected in the decrease of its smallest dimension (thickness
  Thickness
  Thickness may refer to:Thickness may refer to:* Thickness in graph theory* Thickness of layers in Geology* Thickness 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
  Backpack
  A backpack is, in its simplest form, a cloth sack carried on one's back and secured with two straps that go over the shoulders, but there can be exceptions...
  
  . (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
  Hydration pack
  A hydration pack is a type of hydration system built as a backpack or waist pack containing a reservoir or "bladder" commonly made of rubber or flexible plastic. The reservoir contains a capped mouth for filling with liquid and a hose that allows the wearer to drink hands-free...
  
  ), 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
  Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....
  
  .)
• 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
  CamelBak Products, LLC is an outdoors equipment company known primarily for its hydration products, such as hydration packs and water bottles. CamelBak is also a supplier of hydration packs, protective gear, and other products to the U.S. military and law enforcement agencies around the world.The...
  
   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'.

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 tubing to surround the hose may be used to reduce heat transfer between the environment and liquid in the hose, keeping a cold liquid refreshing in summer, or forestalling the system's becoming unusable due to freezing of the contents in the winter.

Bite valve

At least one manufacturer offers a tethered, slip-off, foam cowl that forestalls freezing of the bite valve, and also prevents 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 removing bacterial colonies that may build up 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 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
  Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
  
   and humidity
  Humidity
  Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
  
   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 (usually in combination with flavoring 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 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
  Thermo Scientific Nalgene is a brand of polyethylene plastic developed and manufactured by Nalge Nunc International originally developed for laboratory storage containers. It is now used in the manufacture of water containers, vials, bottles, bags and carboys for packaging, shipping, and storage...
  
  -style bottles during rests.
• On trips over a day, or in especially hot conditions, need for more water than is carried may require purification
  Water purification
  Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...
  
   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 discomfort of drinking from a perfectly sterile
    Sterilization (microbiology)
    Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media...
    
     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, 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.
• 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.

Manufacturers

U.S. manufacturers of ready-to-use hydration systems include:

• SOURCE
• Booby Water Tank
• Capital Safety
• CamelBak
  CamelBak
  CamelBak Products, LLC is an outdoors equipment company known primarily for its hydration products, such as hydration packs and water bottles. CamelBak is also a supplier of hydration packs, protective gear, and other products to the U.S. military and law enforcement agencies around the world.The...
  
  
• Hydrapak
• Mountain Safety Research
  Mountain Safety Research
  Mountain Safety Research, or MSR, is an American corporation located in Seattle, Washington, and owned by Cascade Designs. It was founded in 1969 by Larry Penberthy because he was not pleased with the safety and reliability of outdoor equipment....
  
  
• Nalgene
  Nalgene
  Thermo Scientific Nalgene is a brand of polyethylene plastic developed and manufactured by Nalge Nunc International originally developed for laboratory storage containers. It is now used in the manufacture of water containers, vials, bottles, bags and carboys for packaging, shipping, and storage...
  
  
• Platypus
• MPACK Endurance Gear
• GEIGERRIG