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How to Choose Hydration Packs

Once you’ve used a hydration pack, its benefits become self-evident:

  • Convenience: No slowing down or stopping to reach for a bottle. If you can get the sip tube to stay in place (admittedly, not always an easy task), hydration is a speedy, almost effortless task—just grab, gulp and go.
  • Efficiency and performance: Since water intake is simpler with a hydration pack, you tend to drink more often, and a well-hydrated athlete is a better performing athlete.
  • Cool factor: You can mock your bottle-slurping companions for being the antiquated, time-squandering knuckle-draggers that they are. (Just be prepared for some squirtage when you do.)

    Deciding which hydration pack is best for you is a pretty straightforward process.

    Choose by Activity

    Who should get a pack already equipped with a reservoir? Who might need only a reservoir? What reservoir size and pack size are best? Here are some general preference patterns we’ve noted at REI.

    Activity Most Popular Choices
    Day hikers, backpackers, climbers Reservoir only (2 or 3 liters), or hiker-specific hydration pack
    Trail-runners, racers, fitness walkers Waistpack or minimalist (1L) hydration pack
    Road cyclists focused on speed Small pack or no pack; traditionalists may prefer bottles
    Recreational cyclists Sleek pack with 1L to 2L reservoir and modest cargo space
    Touring cyclists Small to medium pack, but with larger (2L or 3L) reservoir
    Mountain bikers Large pack with ample cargo capacity; 2L to 3L reservoir
    Snowboarders, skiers Small to medium pack, 2L reservoir; insulated sip tubes

    As the name suggests, hydration packs are designed principally to transport water, plus a few small extras—in most cases, that is.

    Some considerations:

    Day hikers/backpackers/climbers: Decide between 2 options:

    1. Choose a pack engineered around a pre-installed reservoir. The reservoir is custom-fitted for the pack, making it easier to access, fill and clean.
    2. Add a reservoir to hydration-compatible pack. Nearly all newer daypacks and backpacks are designed with an interior sleeve that can hold a reservoir (and offers a portal for the sip tube). If that describes an existing pack you own, simply add a reservoir to it. Just make sure the reservoir can fit in the sleeve inside your pack.

    Trail-runners/racers/fitness walkers: Specialized “multisport” packs usually emphasize low weight, small dimensions and stability. Cargo capacity, however, is small—just enough for keys, gel packs and maybe a minimalist wind jacket.

    Cyclists: A key issue: Fit vs. size. Speedsters want a bare-essentials pack that feels light and stable. Long-distance grinders may be more willing to accept a larger load.

    Mountain bikers: All of cycling’s elements—the frames, the tires, the hills, the risks, the thrills—are bigger here, so in general the packs are as well. The extra cargo space often comes in handy.

    Snowboarders and skiers: As with backpackers and hikers, you can either choose a sport-specific hydration pack with insulated components, add an insulated reservoir to an existing pack or “winterize” an existing reservoir by adding, say, a bite valve cover or a reservoir, tube and bite valve cover . Some snowsport-specific packs include lash points or carry straps to allow hands-free transport of a board or skis. Many snowsport packs include insulated reservoirs; some do not.

    Shop REI’s selection of hydration packs.

    Select a Reservoir Volume


    1L or 1.5L (34 or 50 fluid ounces): A good choice for minimalists, kids, short-distance bike commuters, weight-conscious recreational riders.

    2L (68 fl. oz.): The most popular reservoir size offered at REI. It offers a nice balance of reasonable weight and bulk while providing a sufficient quantity of water that in most situations will require only occasional refilling.

    3L (102 fl. oz.): Made for the thirstiest of riders, people disinclined to stop for refills or anyone exploring terrain where water is scarce. Since a liter of water weighs approximately 2 pounds (0.9 kilograms), the potential drawbacks of toting a 3L reservoir (weight and bulk) are fairly obvious. Yet a 3L reservoir offers excellent versatility. To keep weight low on shorter trips, carry only the amount of water you anticipate needing. Then, on the occasions when you need the full 3L capacity, it’s available to you.

    Size of the Opening

    CamelBak reservoirs sized 1L or larger offer a 3.5-inch opening. (A few CamelBak hydration waistpacks use reservoirs smaller than 1L.) This extra-wide opening makes it easy to drop in ice cubes, and many people can fit a hand through the hole to better clean the reservoir’s interior. Reservoirs from MSR use a 63mm (2.5-inch) opening, which matches the screw-on (no-spill) threads of all MSR water filters.

    How Much Water Should You Drink?

    CamelBak recommends 1 liter of water for every hour of activity. Yet any number of factors (temperature, elevation, personal health, activity intensity) could impact a person’s hydration needs.

    In 2004, the Food and Nutrition Board of the nonprofit Institute for Medicine (part of the National Academy of Sciences) released a report on the recommended intake of water (and some minerals). While exact water requirements were not specified, general daily recommendations for women were set at 2.7L (91 fl. oz.) and 3.7L (125 fl. oz.) for men. This figure includes “total water”—water derived from all beverages and foods. About 20% of a human’s daily water intake comes from foods. Exercise intensity and high temperatures clearly will increase a person’s daily water needs.

    Excessive water intake can actually be life-threatening. But by far the greater risk facing active outdoor athletes is under-hydration and dehydration.

    Play it smart. Step up your awareness of body signals when active outdoors, particularly if the intensity, temperature or elevation is higher than normal for you. Drink fluids regularly and generously, even before your thirst-alert mechanism kicks in. Using a hydration system gives you an advantage. Because fluids are so easy to access, you’ll drink more often and as a result perform better.

    Consider Cargo Capacity

    Cargo space in hydration packs varies by intended use.

    The largest backpacking/hiking packs offer close to 2,500 cubic inches (41L) of cargo room and offer enough comfort and load-support features to perform well on light-and-fast overnight adventures. Otherhiking/climbing packs are in the 1,800 cu. in. (29L) range and are well-suited for all-day activities.

    Mountain bike hydration packs are a little smaller, with cargo space ranging from 1,400 cu. in. (or 23L, enough for all-day rides) to 100 cu. in. (3L, just enough room to carry a spare tube, CO2 cartridge, wallet and an energy bar).

    It’s essentially the same story for snowboarders and skiers. Some people want extra cargo room as a stash spot for extra clothing layers. Others want the smallest pack possible so they can wear it under a jacket and use body warmth to keep liquids unfrozen.

    Road bike hydration packs and trail-runner waistpacks tend to be the smallest of the group. The reason: Hydration packs, originally created for cyclists, are meant to carry lightly on a person’s back and generate minimal wind resistance.

    Get a Good Fit

    Bigger is not necessarily better. Lots of cargo capacity can be useful. For cyclists, though, most don’t need much space—just enough room for a jacket, a few tools, a spare tube, snacks and a few other toss-ins. Keep in mind that a bigger pack is less aerodynamically efficient.

    Stability. Smaller packs will be more stable on your back. Envision a pack when it’s fully loaded and how it will ride on your back. If you anticipate carrying large loads, look for a waistbelt.

    Organization. Run through a mental inventory of the gear you carry. Can the pack accommodate your favorite jacket? Does it offer a pocket where a potentially gunked-up tool can be isolated from other items? Does it provide enough snack space for your length of trips?

    Women’s and kids’ models. Some styles are engineered to provide an enhanced fit for a women’s physiology or a younger person’s smaller frame.

    Sip Tubes and Bite Valves

    Sip Tubes

    All brands offered at REI use tubes constructed out of polyurethane, a durable and tangle-free material. Polyurethane, though, can transfer some taste of plastic to the water.

    To minimize this, make an effort after every trip to ensure the tube’s interior dries completely. If it detaches from the pack, disconnect the tube and shake out all the water that you can.

    Direct exposure to sunlight for a limited length of time can help dry a tube, though try to avoid selecting an incessantly sunny spot where heat can build up and cook the tube. Instead, seek a well-ventilated location.

    Bite Valves

    Silicone is a commonly used material. Modest tooth pressure, not a big chomp, is usually all that is needed to get water flowing. Some people routinely bite too hard on their valves and hastily wear them out. Our sales staff has heard that bite valves that twist on and off, or that have an on/off switch, are less prone to leakage.

    Bite valves seem to be an area of hydration systems most vulnerable to leaks—not surprising since they get most of the action. It is not uncommon to need to replace a bite valve once or twice in the lifetime of a hydration system.

    Other Components

    Tube portals: This is a slit (or slits) that allow your sip tube to easily thread the sip tube from the reservoir inside the pack to the exterior. Many packs offer 2 portals so you can position the tube to hang over either shoulder. Some packs offer a single, centered portal. You may find a pack that has 1 portal on 1 side of the pack. If you have a strong preference where your tube hangs, choose a pack with a portal system suited to your wishes.

    Clips: Looking for a way to keep your tube positioned for easy access? CamelBak offers accessories such as the CamelClip, Tube Director and Tube Trap.

    Cold weather add-ons: As mentioned earlier, assorted winterized add-ons are available, including insulated sip tubes, insulated reservoirs, reservoir covers and bite valve covers. They can be handy, though they add a little bulk and weight to your system.

    Usage Tips

    Frigid weather: 1) Fill the reservoir with warm water to resist freezing. 2) Routinely perform a “blow back” in your sip tube when you’ve finished a water break. If you push water out of the tube and back into the reservoir, water can’t linger in the tube and freeze.

    Hot weather: It is OK to freeze a reservoir and its contents. Just be sure to leave room (perhaps one-quarter of the reservoir’s capacity) for the liquid to expand as it solidifies. Do not fill the reservoir to the brim and then attempt to freeze it. If you do and then seal the reservoir, it could potentially burst. You can also use an insulated reservoir and tube to preserve the temperature of cold water on hot days.

    Note: All hydration reservoirs offered at REI, whether sold separately or included in a hydration pack, are BPA-free.