The Best Hydration Packs for Day Hikers

This pack is solid, affordable, and comfortable, even without a fancy suspension system, and the 2.5-liter hydration system is simple to use. It’s small enough to make a good around-town pack, too.

*At the time of publishing, the price was $80.

Our pick

Osprey Skimmer 16

The women’s version of the Skarab, this pack equally impressed our testers with its comfort. Slightly smaller than the Skarab, it still holds what you need for a medium-length hike.

Our favorite hydration daypacks for moderate hikes are the Osprey Skarab 18 (for men) and Osprey Skimmer 16 (for women). Our testers were ready to trade in their old daypacks after trying these straightforward, rugged packs, the smallest in Osprey’s minimalist Skarab/Skimmer series. They don’t have a lot of extra pockets or sophisticated suspension systems, but they’re comfortable when used with moderate loads. Both packs come with Osprey’s 2.5-liter reservoir, which we found to be reasonably easy to fill and clean. These models fit the bill for people who want hydration combined with a well-constructed, no-fuss backpack.

Runner-up

Osprey Syncro 15

Straddling the line between hiking and biking, this high-tech pack features a cooling, comfortable suspension system.

The

Osprey Synchro 15

is a great choice for people who might be hiking in hotter climates or who want to use one hydration pack for multiple sports. Unlike the Skarab and Skimmer, but like Osprey’s larger packs, the Synchro rides on a mesh back panel that provides excellent ventilation and comfort. Although designed in the long, narrow shape of a cycling pack, it has plenty of room for hiking gear.

Upgrade pick

CamelBak Fourteener 24

This large but comfortable daypack easily holds its 3-liter bladder and all the gear you’ll need for an ambitious outing.

This pack easily lives up to its name; it’s plenty big and rugged enough for an all-day assault on one of Colorado’s famed 14,000-foot peaks. For men looking to carry multiple extra clothing layers, lunch, camera, and other odds and ends—in addition to plenty of water—the

CamelBak Fourteener 24

hit the sweet spot in terms of capacity, useful features, and comfort. The pack’s 3-liter reservoir is one of the largest you can buy, and it’s easy to use. Our testers especially liked this pack’s semi-rigid back panel suspension system, which handled heavy loads with ease.

Upgrade pick

Osprey Mira AG 18

Innovative elements—including the “anti-gravity” hip belt and mesh ventilation panel—plus plenty of room for gear and effortless hydration—made this the top choice for longer hikes.

The

Osprey Mira AG 18

is a beautifully engineered, fully featured, and very comfortable large daypack. It includes a 2.5-liter reservoir and features a rigid suspension system and padded waist belt that helps it support relatively heavy loads—and helped it become the favorite pack of our female testers. They also found its hydration technology easy to use.

Budget pick

CamelBak Arete 18

Small enough to stuff into a suitcase, this pack contains a 1.5-liter reservoir, perfect for staying hydrated during days of sightseeing and light hiking.

For people who want a basic, lightweight hydration pack—one that’s affordable as well as perfect for traveling—we recommend the

CamelBak Arete 18

. Constructed with relatively thin nylon and minimal padding, this pack easily folds up to tuck into your luggage, yet it’s comfortable when carrying modest loads. Its 1.5-liter reservoir holds just enough water for a pleasant afternoon sightseeing in a foreign city or strolling along an easy trail.

Why you should trust us

We spent 50 hours researching hydration packs online and then testing them on our own backs—and those of our hiking friends—mainly on the rugged trails of the Hudson Valley, including the portion of the Appalachian Trail that runs through New York’s Fahnestock and Harriman state parks. We interviewed sports nutrition consultants, outdoor retailers, accomplished hikers, and professional guides. We scoured the literature on hydration and researched the relative advantages of packs versus water bottles. And we read numerous reviews by professionals on sites including Outdoor Gear Lab, Backpacker, and Outside Online, and by users on sites such as Amazon and REI.

As avid outdoors people and lifelong water drinkers, we began using hydration systems when they first appeared in the 1990s. Jim purchased early versions of the CamelBak and HydraPak systems for mountain biking and then for other sports, including skiing, hiking, and backpacking. After spending several years sharing germs on Jim’s bite valve (along with those of our kids), Jenni finally broke down and got her own hydration system for mountain biking and hiking. Several generations of these packs have kept the family hydrated in environments ranging from the Grand Canyon to the Argentine rain forest to the frigid slopes of the Grand Tetons. As a journalist, Jim spent 10 years as the editor-in-chief of Popular Mechanics magazine, and he has worked at National Geographic Adventure and other titles. Jenni is a former weekly newspaper editor and math teacher. (Yes, we’re married.)

Who this is for

Do you drink water? Do you like to have fun outside? You might need a hydration system.

Here’s why hydration matters so much for people with active outdoor lifestyles. Water represents between 45 and 65 percent of a person’s body weight. A 150-pound adult man or woman contains roughly 40 liters of water—more than 10 gallons. What’s more, we lose between 5 and 10 percent of that water every day, even when we’re not exercising. When we are, we can lose more than one liter of water per hour in sweat alone.

Most of the time, your body does a great job of managing your internal water level. If it falls too low, you get thirsty. Drink more than you need, and your kidneys will get rid of the surplus as urine. Things get more complicated when we begin to work hard. As we sweat to stay cool, our bodies often struggle to keep up. According to Monique Ryan, a sports nutrition and hydration expert who has advised elite runners and cyclists, even casual hikers can fall behind on their water needs. “It’s really easy to get dehydrated even if you’re just out there for an afternoon hike,” she says.

Fortunately, mild levels of dehydration are no big deal over short periods of time. “Studies show you have to be dehydrated by about two percent of your body weight before it begins to affect your performance,” Ryan says. (For most adults, that means being somewhere between one and two liters below your optimal water level.)

As we sweat to stay cool, our bodies often struggle to keep up. Even casual hikers can fall behind on their water needs. “It’s really easy to get dehydrated even if you’re just out there for an afternoon,” says sports nutrition expert Monique Ryan.

If you keep pushing yourself without replenishing that water, however, bad things start happening. Hard exercise combined with dehydration may lead to headaches, fuzzy thinking, and nausea. Some of the water that your body is losing comes out of your bloodstream: Your blood volume falls, your heart has to work harder, and your performance starts to suffer. Not having enough water in your system also means that, eventually, you’ll have trouble producing sweat, and a vicious cycle of overheating can set in. Severe levels of dehydration can lead to an elevated core temperature, convulsions, and even death.

But going wildly overboard on hydration can also be dangerous. Heavy overconsumption of water over several hours can lead to a scary condition called hyponatremia in which the body has too much fluid and not enough sodium. In response, the body’s cells—including brain cells—swell up like balloons. Eventually, the brain expands inside the skull, which can lead to unconsciousness and, yes, death. There have been fatal cases of hyponatremia among marathon runners, U.S. Army trainees, Grand Canyon hikers, and even radio station contestants. Here’s the bottom line: “Drinking too much and drinking too little can both be fatal,” says Alex Hutchinson, the “Sweat Science” columnist for Runner’s World magazine. “Fortunately, both extremes are very rare. And when there is a fatality, there are usually other health issues involved.”

The best reason to carry a good hydration system is to make sure you enjoy your outdoor activities. Without enough water, your hike stops being fun.

The solution is to use common sense: Do drink when you’re thirsty and don’t force yourself to drink more than feels comfortable. “You don’t need to be obsessed,” Hutchinson says, “but you do need to plan for hydration and think about where you’re going.” Hikers venturing far from civilization—especially in desert conditions—should always carry a comfortable reserve. Backcountry guide Jacques Hadler, who’s based in Utah, advises his clients to carry one liter of water for each hour of strenuous activity. That’s a good baseline until you learn how much your body needs in various conditions. (For those who want a more precise estimate of their water needs, here’s some guidance on how to calculate your “sweat rate.”) Remember, carrying a little more than absolutely needed could be a lifesaver if you get injured or lost. But leaving survival scenarios aside, the best reason to carry a good hydration system is to make sure you enjoy your outdoor activities. Without enough water, your hike stops being fun.

Okay, so bringing along enough water is important. But what’s wrong with just carrying a water bottle in your pack? Nothing. But many hikers and other outdoor athletes agree with Scott Yorko, a former editor at Backpacker magazine. “Water bottles are a pain in the ass,” he says. “It’s way easier to stay hydrated when the water is three inches from your face.” That’s why backpack hydration systems are a key tool in Yorko’s multi-sport lifestyle.

A pack-based hydration system is a backpack containing a soft, removable water reservoir, or “bladder,” that has tubing and a bite valve that enable easy, hands-free, and continuous access to water. (We say water because nothing but water should be used in the reservoirs. More about this later.) The water reservoir lies in the back of the pack, in a dedicated pocket. In most cases, it is a long, somewhat flat bag that runs vertically down the length of your back. The drinking tube is attached to the bottom of the reservoir, providing pressure for easier drinking. The tube emerges through an opening at the top of the bladder pocket and runs through loops along the shoulder strap. The bite valve at the end is held in place in front of the chest by a clip or (much more cool!) a magnet. All of the hydration systems we recommend in this review are BPA-free, although, to be honest, BPA is not something you really need to worry about. A large-scale risk assessment conducted by the European Food Safety Authority (which has much stricter standards than the US Food and Drug Administration) found that BPA poses virtually no threat—even to young children. (For a further discussion of the safety of plastic drinking systems, see our review of the Best Water Bottles.)

Another advantage to backpack systems lies in how they carry the load. A long hike in warm weather can easily require 3 liters, or 6.6 pounds, of water. Jamming one-liter water bottles into a daypack can make for an awkward, poorly balanced load, and even if you have side pockets for bottles, they can be hard to reach. But a soft-walled 3-liter reservoir that fits close to your back puts that load in the most comfortable position.

One note: Even if you already own a hydration pack, you may want to consider getting a new one. Having ourselves relied on systems that are between several and way-too-many years old, we were surprised by the improvements in comfort and usability that we saw in the newest packs.

How we picked and tested

In recent years, hydration systems have become so popular that even backpack makers that don’t provide reservoirs with their packs do include sleeves and slots so that a bladder can be added later. For this guide, we limited our evaluations to packs that are sold with reservoirs included. We also focused on packs designed for single-day hikes rather than longer excursions. Anyone searching for a multi-day backpacking pack has other concerns that are at least as important as the hydration features.

We surveyed reviews of hydration systems from such sites as Outdoor Gear Lab, Backpacker, and more. We also perused user reviews on Amazon and elsewhere. And we interviewed retailers, backcountry guides, and expert and intermediate users. In selecting packs for hands-on (or on-back) reviewing, we prioritized top-reviewed models. There are scores of hydration packs on the market today from a wide range of manufacturers. Some companies make a small number of packs aimed at specialized users, such as snowboarders, some of which are quite good. (Feel free to let us know in the comments if you have a favorite among these sorts of products.) But our selections tilted toward the most established brands, whose packs are widely available.

The reservoir in one cheap pack we tested features a detachable drinking hose, just like those on fancier packs, except—oops!—the fitting that connects to the reservoir doesn’t have an internal shut-off valve. So removing the hose mid-hike means creating a mini-geyser in your pack.

The brand-name packs that dominate this field are fairly expensive, ranging anywhere from $80 to $160. We looked for cheaper alternatives (some of which we describe in our competition section below), but we can’t recommend the ones we tested for two main reasons. The first was overall quality. Although some of these inexpensive alternatives look a lot like higher-priced packs, closer inspection revealed shoddy workmanship and poor materials. A plastic fitting on one pack broke the first time we tried to use it. Reservoirs were harder to close securely, which led to leaks. One reservoir features a detachable drinking hose, just like those on some Osprey and CamelBak bladders, except—oops!—the fitting that connects to the reservoir doesn’t have an internal shut-off valve. So removing the hose mid-hike means creating a mini-geyser in your pack.

We also found that these low-cost packs imparted unpleasant flavors to the water they carried. And those flavors were definitely worse when we left the bladders filled overnight. It’s true that even high-end hydration systems sometimes suffer from this problem. But none of the more expensive packs we tested came close to having flavor problems at this level. We should be clear that this is a palatability issue rather than a health concern: Every material designed to come into contact with food or drinking water—including the plastic components of hydration reservoirs—is regulated by the US Food and Drug Administration. The FDA rules require that any “individual compounds that migrate into food (including drinking water) must be authorized,” according to an FDA spokesperson. Of course, just because those compounds are considered safe doesn’t mean they’re desirable. Leading reservoir makers put a lot of effort into minimizing the flavor problem. “We constantly do blind taste tests on materials,” Samuel Lopez, vice president of product at HydraPak, told us. (HydraPak is a leading manufacturer of hydration technology—providing bladders to Osprey, Patagonia, Dakine, and others—as well as selling its own line of reservoirs.)

For very casual use, these inexpensive packs might work fine, but we don’t see the point of having a hydration system that you don’t want to drink from. Since having a pack that doesn’t break or leak can be a safety issue in the wild, we can’t recommend them to anyone who plans to actually rely on a hydration system.

A good hydration pack for a three- or four-hour hike needs to excel in four main areas:

  • The reservoir must be easy to fill and clean, the drinking tube and bite valve have to function well, and the water inside shouldn’t pick up any strong, unpleasant plastic flavors.
  • The pack needs to have enough room for trail food, clothes, and incidentals.
  • The pack should feel comfortable with a full load of water and gear, even after several hours on the trail.
  • Its materials and construction quality have to be top-notch, since hydration packs often put up with a lot of abuse in harsh environments.

Our testing regimen began with evaluating each pack’s reservoir with regards to taste, ease of use, filling, drinking, and cleaning. We tested the integrity of the reservoirs’ seams and fittings by filling each one with water and then subjecting it to 100 pounds of pressure while watching for leaks. (All the reservoirs we tested passed this harsh challenge.) We also allowed each full reservoir to freeze solid overnight and then checked for damage after each thawed. (No, they aren’t designed to handle this sort of treatment. But it’s easy to accidentally leave a pack in the car overnight in the winter. And, again, they all survived.)

A pack’s weaknesses—those nagging pressure points, or a lack of balance—reveal themselves more quickly when you’re carrying a full load.

We then tested each pack over dozens of hours of hiking, mostly on the trails of the New York’s lower Hudson Valley. A delightfully unseasonable stretch of 70-degree weather in February allowed us to gauge the effectiveness of the packs’ ventilation systems on the beaches and trails of Long Island’s wild eastern tip. And a late-season blizzard gave us the chance to try out many of the packs while cross-country skiing. (Though winter sports are not a primary focus of this review, we feel that a good hydration pack should be versatile enough for a variety of activities.) We also recruited some experienced users to help with our tests. These included members of the Intrepid Men’s Hiking Club (actually co-ed and named with tongue in cheek) that take ambitious hikes in the Hudson Valley every weekend, year round.

Before heading out, we tested each pack’s carrying capacities by filling it with a standard assortment of gear suitable for a half-day hike:

  • Warm insulation layer
  • Rain shell
  • Hat
  • Gloves
  • Lunch and trail food
  • Small survival kit
  • Small first aid kit
  • DSLR camera
  • Incidentals (phone, sunglasses, headlamp, pocket knife, etc.)

When evaluating the all-day packs, we included warmer garments and about twice as much food. In all cases we looked to see how well the packs accommodated the gear—not just whether there was enough room, but how everything fit into the various pockets and pouches. We always tested packs with full reservoirs (even when we knew we wouldn’t need that much water), and sometimes added extra weight as well. A pack’s weaknesses—those nagging pressure points, or a lack of balance—reveal themselves more quickly when you’re carrying a full load.

We followed the manufacturer’s designations when specifying “men’s” and “women’s” packs. Designated women’s packs are designed for women’s smaller average stature and, it is claimed, for women’s “geometry” as well. However, taller women may be most comfortable in a men’s pack, and this may work the other way for men as well.

Our pick

Osprey Skarab 18

This pack is solid, affordable, and comfortable, even without a fancy suspension system, and the 2.5-liter hydration system is simple to use. It’s small enough to make a good around-town pack, too.

*At the time of publishing, the price was $80.

Osprey Skimmer 16

The women’s version of the Skarab, this pack equally impressed our testers with its comfort. Slightly smaller than the Skarab, it still holds what you need for a medium-length hike.

Our choice for moderate-length hikes, the Osprey Skarab 18 (sized for average men) and the slightly smaller women’s version, the Osprey Skimmer 16, combine good hydration with a relatively spacious, comfortable, simple pack, all for an affordable price. Both versions of the pack include Osprey’s 2.5-liter Hydraulics reservoir—which leaves 15.5 liters of storage available when the bladder is full. (Get it? 2.5 + 15.5 = 18) These are manufactured for Osprey by Hydrapak, a leading maker of reservoirs for various companies.

We found these bladders easy to fill and drink from and fairly easy (though not the easiest) to clean. We did note a very faint flavor added to the water when we left the reservoir filled overnight. But this wasn’t the unpleasant plastic-y aroma we experienced with some other brands, and that flavor faded after we’d used the pack a few times. Both packs also incorporate a quick-to-secure magnet that can be used to park the drinking tube on the sternum strap.

Though designed for shorter outings, these packs are not small. We were able to fit an insulating layer, shell, hat, gloves, survival and first aid kits, and lunch, in addition to a full 2.5-liter hydration bladder. There is also bungee cording on the outside of the packs where you can stuff a shell, say, or an extra fleece. So, while they’re not intended for heavy loads, the Skarab and Skimmer have enough capacity for even a full-day hike in mild conditions.

Unlike many of Osprey’s higher-end packs (including the Manta and the Mira, mentioned below), the Skarab and Skimmer don’t have a fancy suspension/ventilation system. The back panel is mesh-covered die-cut foam, and there is a simple web waist belt, not a load-bearing hip belt. Our testers found the design to be perfectly comfortable when carrying loads of 15 to 20 pounds (Osprey says its “load range” is 10 to 25 pounds), but, yes, a little sweatier on warm days than more-ventilated alternatives. What distinguishes the women’s model from the standard pack apart from size—the Skarab is designed to fit an 18- to 22-inch torso, whereas the Skimmer is designed for the 15- to 19-inch range—is a female-specific fit. According to the manufacturer, “the Skimmer’s pack shape is narrower and deeper, allowing greater freedom of movement, and increases stabilization by lowering the position of the load to a women’s center of gravity,” and “the shoulder harness is designed with different curves to create an anatomical fit for a woman’s neck, shoulders and chest.” Our female testers just called it comfortable. As with most of the packs we tested, the sternum strap linking the two shoulder straps can be adjusted up or down for comfort, a feature our female testers appreciated.

Compared to many of the packs we tested, the Skarab 18 is almost minimalist, similar to a traditional climber’s rucksack. It has only one undivided main compartment and one (nicely padded) pocket for sunglasses and other incidentals. One detail that we loved was that, as on all of the Osprey packs we tested, the zipper pulls are substantial loops. Two stretchy-mesh side pockets are good for stashing gloves or a hat. But that’s it; if you like a lot of small pockets and extra straps, this might not be the pack for you.

All this simplicity comes with an added benefit: At about $80 at the time of writing, the Skarab is a lot more affordable than Osprey’s more tricked-out models. If that still seems like a lot to spend on a daypack—and there are certainly plenty of packs available for less—you might want to factor in Osprey’s “All Mighty Guarantee.” Aside from the reservoir (which is only covered for a year), the company promises to repair or replace the pack if it suffers any sort of damage or defect—forever.

Flaws but not dealbreakers

The reservoir that comes with this pack doesn’t include the cool detachable drinking tube found on Osprey’s more-expensive lines of packs, but we had no trouble getting the bladder in and out of the pack, thanks to the well-designed sleeve. The foam back panel isn’t as cool (temperature-wise) as the mesh panels on some of the more expensive packs we tested, so this model might not be the top choice for desert hiking. The bite valve can be turned off (to prevent leaks during transport) by rotating the barrel. While it works fine, you’ll need two hands to do so, and it’s tricky to see at a glance whether the valve is on or off.

Runner-up

Osprey Syncro 15

Straddling the line between hiking and biking, this high-tech pack features a cooling, comfortable suspension system.

The earliest hydration systems were intended mostly for mountain bikers, and that biking-oriented pack design—long and thin, rather than barrel- or teardrop-shaped—remains popular for other sports as well. The Osprey Synchro 15 offers that versatile configuration in a pack that is equally at home on a hiking trail, bike path, or cross-country ski track.

A key factor that sets this pack apart from Osprey’s Skarab and Skimmer is the suspension. Where those packs use a foam back panel that’s in direct contact with your back, the Synchro has a mesh panel, stretched over a lightweight metal frame. Osprey’s larger hiking packs (like the Mira 18—see below) are renowned for their high-tech mesh suspension systems, and the Synchro brings that sophistication to a smaller daypack. Our testers found the pack comfortable both for hiking and biking. The well-designed waist belt keeps it stable, and the mesh back panel stays cool. For anyone who spends a lot of time hiking in hot weather, the Synchro’s superior ventilation might make it a better choice than the Skarab/Skimmer. (The Synchro isn’t available in male/female versions. However, it does come in a slightly smaller S/M version that is two inches shorter than the M/L version we tested.)

The Synchro’s version of the 2.5-liter Hydraulics reservoir includes the clever Quick-Connect valve, which allows you to disconnect the drinking tube at the top of the reservoir. This comes in handy when you are removing the bladder for refilling: you can leave the upper half of the drinking tube attached to the pack and avoid the minor hassle of rethreading the tube through the tube-holding tabs on the shoulder strap. Overall, we found the Hydraulics reservoir easy to use and reasonably easy to clean, though the bite valve shut-off is a bit tricky. As with other Osprey packs, the drinking tube attaches to the sternum strap with a neat little magnet.

The Synchro includes some features specific to cycling like a slot to hold a bike pump and a handy toggle that attaches your helmet neatly to the back of the pack when you’re not wearing it. But it also offers features that are more oriented to hiking. At the bottom of the pack, where Osprey’s more bike-oriented packs include a roll-out tool pouch, this pack has an integrated rain cover. The pack also contains an outer pocket for incidental items (as well a padded pocket for phone or sunglasses) and two small mesh side pockets.

People who intend to also use their hydration pack as a daily around-town pack should note that the narrow design of the Synchro makes it hard to fit a full-size laptop. All those extra features also mean this pack is significantly more expensive than the simpler Skarab/Skimmer models—though not as expensive as some biking-specific packs. (Our guide to mountain-biking hydration packs will be posted soon.)

Upgrade pick for men

CamelBak Fourteener 24

This large but comfortable daypack easily holds its 3-liter bladder and all the gear you’ll need for an ambitious outing.

Named in honor of the 53 peaks in Colorado peaks that top 14,000 feet, the

CamelBak Fourteener 24

is, as its name suggests, the perfect size for a long, challenging hike. Equipped with the full-size hydration reservoir you’ll need for all-day outings, this pack is capable of carrying heavier loads and distributing those loads comfortably on the body, thanks to its full suspension system and backpacking-quality hip belt.

The Fourteener comes with CamelBak’s 3-liter Crux reservoir, an update to the company’s traditional reservoir design that features an easier-to-close cap, and a larger diameter drinking hose, which the company claims delivers 20 percent more water per sip. Our tests didn’t prove that the system delivers more water, but we did perceive that we got the same amount of water with less effort,

which was good enough for us

We also liked this system’s excellent shut-off valve, which (unlike the Osprey valve) makes it easy to see at a glance whether it is open or closed. Overall, we think the Crux reservoir is a solid upgrade to an already-good design. The folks at The MTB Lab shared our opinion of the Crux,

calling it “drastically improved.”The reservoir fits in its own insulated sleeve inside the pack and was easy to insert even when the pack was fully loaded. And, as the drinking tube is detachable, you can disconnect the tube when removing the bladder for refilling. That means you won’t need to re-thread the tube through the various slots and straps each time you need to add water.

One of our experienced testers praised the Fourteener’s “ease of expandability.” When the pack is lightly loaded, compression straps keep its profile slim and close to your back; loosen those straps and you have room for much more gear. Even when you think the pack is full, an expandable front pocket allows you to stuff in a few more soft items. (Besides the 24-liter configuration, the Fourteener also comes in a 20-liter size.)

The Fourteener includes a plethora of specialized compartments and features, including straps to carry an ice axe and trekking poles, and a padded pocket for delicate items like phones and sunglasses. Compared to many daypacks, the Fourteener has a particularly rigid design. Both a stiff pad sits comfortably at the base of the spine and a padded hip belt help distribute the load. Two additional foam- and mesh-covered horizontal pads—one at the mid-back and one that rides between the shoulder blades—keep the pack away from your back, providing excellent ventilation. This somewhat unusual suspension puts the weight primarily on the back of the pelvis rather than on the sides of the hips. The best alternative to the Fourteener, Osprey’s Manta AG 20 (see The competition below), offers a more traditional hip belt that puts more weight on the outer hips. Both were comfortable, but our male testers preferred the CamelBak approach. They also liked the Fourteener’s more robust belt and buckle design.

The Fourteener’s sturdy construction results in a pack that’s on the heavy side (just over three pounds, by our measurement) and perhaps over-engineered for the casual user. But we think the tradeoff is worth it for serious hikers. Our only other quibbles: The small, zippered pocket on the waistbelt isn’t big enough for a smartphone, and, unlike Osprey’s Manta, it doesn’t include a rain cover.

Upgrade pick for women

Osprey Mira AG 18

Innovative elements—including the “anti-gravity” hip belt and mesh ventilation panel—plus plenty of room for gear and effortless hydration—made this the top choice for longer hikes.

Our female testers found the Osprey Mira AG 18 “amazingly comfortable,” which is the main reason it is our pick for women’s all-day pack. Overall, this is a high-capacity pack with an easy-to-use hydration system and loads of smart features. The AG stands for pack’s “anti-gravity” suspension system. Osprey has long been known for its innovative suspension designs that maximize adjustability and ventilation, and the Mira reflects that heritage. (Osprey also makes a slightly larger version of this pack for men, the Manta, which we cover below, in The competition.)

What is most surprising is how a pack that looks so confining can be so comfortable. The hip belt appears to be a wire cage, covered with fabric and foam, that encircles your body, which you have to wedge into the opening before you close the belt with a web strap and buckle. But then, surprise! Somehow the weight of the pack—including a not-insubstantial 5.5 pounds of water when the 2.5-liter bladder is full—is so evenly distributed, it feels like there isn’t much weight at all. The ventilation system is another revelation—and a reason why so many of the Appalachian Trail through-hikers we met in the White Mountains last summer were carrying larger Osprey packs with the same feature. Before you put it on your back, the system appears to be a flexible mesh stretched over a frame that holds it an inch away from the back of the pack.

Where our male testers generally preferred the CamelBak Fourteener’s design for comfort, our women hikers decisively opted for the Osprey Mira.

The mesh compresses when you’re wearing the pack. Behind the mesh is a layer of perforated foam that ensures the pack is not pressing on the length of your back. The closest runner-up to the Mira is CamelBak’s female version of the Fourteener, called the Sequoia 22 (see The competition, below), which uses the same firm, three-panel suspension featured on the male-oriented pack. But where our male testers generally preferred the CamelBak design for comfort, our women hikers decisively opted for the Osprey.

Another advantage of the Mira over the Sequoia is that the tube on this 2.5-liter Hydraulics reservoir has the same QuickConnect feature as the Synchro 15 (above)—though with a pack this size, we would have preferred a 3-liter reservoir. And as in the Synchro (and the Skarab and Skimmer), a magnet on the chest strap holds your drinking tube in place.

The Mira comes with all the bells and whistles (actually, pockets and zippers) expected in a full-day pack. The pack features one main pocket, which was big enough for additional clothes and all the other gear on our packing list, even when a full bladder sat in the pocket behind. (Besides the 18-liter version, the Mira also comes in 26 L and 34 L versions.) An outer zip pocket, three stretch pockets, and a phone/shades pocket hold gear that you need to get at quickly. Two small zip pockets on each side of the front of the belt have room for little items you might need while moving, such as folding binoculars or a (medium-sized) smartphone. Four compression straps let you carry a smaller load closer to your body. The pack comes with a rain cover housed in its own pocket. Trekking-pole loops at the side of the pack enable you to stash your poles without taking off the pack.

Budget pick

CamelBak Arete 18

Small enough to stuff into a suitcase, this pack contains a 1.5-liter reservoir, perfect for staying hydrated during days of sightseeing and light hiking.

When we first saw the CamelBak Arete 18, we questioned whether its lightweight design could go the distance as a hydration pack. Constructed with fairly thin nylon and little padding, it didn’t look like the kind of rugged, highly engineered hydration pack we’re used to. And that’s exactly why we fell in love with it. All of the other packs in this guide are constructed with bulky, stiff materials. That’s great when they’re on your back. But say you’re going to Asia or South America and plan to hike. Unless you want to also use your hydration pack as your carry-on bag, you’ll be tempted to leave it behind. Most hydration packs are just too awkward to pack in your luggage. The Arete is so lightly constructed, you can easily tuck it into your suitcase. Once you get to your destination it makes a fine, lightweight daypack for knocking around town and moderate hikes.

The Arete comes with the 1.5-liter size of CamelBak’s new Crux reservoir, which was a top performer in our tests (see above). Apart from size, the only difference between the Crux used in this pack and the version we saw in our Upgrade pick for men, the CamelBak Fourteener, was that this version doesn’t have a detachable drinking tube. (It still features the shut-off valve we liked so much in the Fourteener’s Crux.)

This is an unconstructed pack with just two outside pockets and no waist strap—it wouldn’t be very comfortable with a heavy load. But we found it perfectly easy to carry on a long afternoon exploring the trails and beaches of Montauk, Long Island. (In addition to the 18-liter size, it also comes in a 22-liter model. We didn’t test that, but we suspect that if we needed to carry that much gear, we’d probably want a more comfortable suspension system.) Another drawback of the lightweight materials is that the Arete isn’t designed to stand up to a lot of rough treatment. Most of the other packs we tested are more stoutly made—but also heavier and bulkier.

The competition

Osprey Manta AG 20: Brother to the Mira, this is a comfortable, well-engineered hydration daypack that includes some features—like an integrated rain cover—that the CamelBak Fourteener lacks. So why did we pick the Fourteener as our Upgrade choice for men? It came down to a difference in water capacity (the Manta comes with a 2.5-liter reservoir compared to the Fourteener’s 3 liters), some small differences in features, and our male testers’ preference for the CamelBak’s suspension system. But pack comfort is a personal thing; your mileage may vary.

CamelBak Sequoia 22: This is the women’s counterpart to the men’s Fourteener, suitable for a “big-day” hike. It is a well-made pack with plenty of capacity, and it includes a slightly bigger reservoir than the Osprey Mira that we recommended. However, our female testers found CamelBak’s NV ventilation system—three rigid foam- and mesh-covered bars—to be less comfortable than the Osprey design, even though it ventilated just as well.

Camden Gear Hydration Pack: $27 at the time of writing, this hydration pack is one of the top sellers on Amazon, and we tested it as part of our quest for a budget pack. It is large enough for a 2-liter bladder and has a little space for additional items, plus a small bungee configuration on the outside of the pack that can hold extra garments. However, we couldn’t get over the fact that the water from its bladder tasted terrible off the bat and even worse after it sat in the pack for a few hours. This taste faded somewhat after several cycles of cleaning and use but remained noticeable.

Unigear Tactical Hydration Pack: Another Amazon top seller and a budget contender, this pack is billed as tactical, which means, that despite being inexpensive, it is claimed to fit military specifications. Unlike most packs, which are made from fairly light nylon, it is constructed out of a heavy-duty polyester material, and it weighs nearly two pounds (that’s almost twice the weight of our top picks, the Osprey Skarab and Skimmer). Here, too, serious problems with water flavor persisted even after cleaning.

High Sierra Piranha: Another budget-pack contender, this pack also suffered the serious flaw of bad flavor. It is more fully featured than other budget packs, with a larger storage pocket and a zip-out panel for overflow belongings that can be clipped to fittings near the top of the pack.

High Sierra Propel: The Piranha’s little sister, the Propel unfortunately uses the same unsavory bladder. It has less storage space than the Piranha but does include the zip-out “overflow” panel. However, one of those clips on our test model broke the first time we tried to use it.

Care and maintenance

Caring for the “pack” portion of your hydration pack is a matter of taste. Some of us are quick to spot clean any smudge of dirt or mud. Others wear those marks proudly as testaments to a pack well used. Caring for the “hydration” portion is another matter. You want to make sure that your hydration reservoir/bladder can provide you with clean water on every outing.

1) Never use your bladder for any fluid except water. It is difficult to fully rinse sports drinks and juices from these narrow containers, and any residual sugar is going to encourage bacterial growth. (This goes double for all you folks trying to smuggle wine into that outdoor music festival.) If you must use a sports drink in your hydration pack, consider buying a second bladder just for that purpose—and be extra vigilant about cleaning it. (The Israeli manufacturer Source makes a two-compartment reservoir it calls D/vide, which uses two separate drinking tubes and allows users to simultaneously carry a sports drink and pure water. We haven’t tried it, but it’s a clever idea.)

2) The most important step in reservoir maintenance is to let the inside of the bladder dry thoroughly after each use, which requires some way to hold the bladder open so air can circulate. Some bladder manufacturers sell drying racks configured for their products, such as this one for the CamelBak Crux reservoir or the one that comes with this cleaning kit from Osprey. For years, however, we have managed to make do with a wire hanger bent at one end in a zigzag shape to hold the sides of the bladder apart and at the other end to let us hang the bladder upside down so that residual water can drain. (You can also insert the cardboard tube from a used-up roll of paper towels to hold the bladder open.) Even then, some reservoir designs—including CamelBak’s—let water collect in the seam below the cap. Gear expert Scott Yorko recommends twisting a sheet of paper towel into a wick and inserting that into the bladder to help it dry. Even after the reservoirs are dry, we like to store them hanging in a dry place, rather than stuffed in a pack where mildew might develop. For most users, proper storage will allow the system to stay fresh for long periods between cleanings. “If you normally fill it with chlorinated tap water, that ensures that the bladder is a pretty sterile environment,” notes Moab guide Jacques Hadler.

3) When it’s time to give your reservoir a deep cleaning, there are several approaches. The first thing to remember is, don’t overdo it: Strong solutions of bleach will leave an aftertaste (not to mention possibly being hazardous to your health!), and boiling water can damage the bladder. A gentler approach is to mix a couple of tablespoons of baking soda with hot water in the bladder, the drinking tube, and bite valve. Let the mixture sit for an hour and then drain and rinse. For a more aggressive clean, you can use a mild bleach solution (one teaspoon of bleach for three liters of water) and pour that through all the components. (Bite valves can also be removed and washed separately.) Then wash the bladder with a few drops of mild soap and plenty of hot water. (Note that Osprey advises against using bleach in their products, while CamelBak recommends a mild bleach solution.) If possible, reach into the bladder itself and scrub lightly with a cloth. A tube brush like this one will help you scrub the drinking tube as well. Leading hydration system manufacturers sell foaming cleaning tablets, or, for the more obsessive, entire cleaning kits, which usually include a tube brush. Some users swear by denture cleaning tablets as a cost-effective approach. We prefer HydraPak’s Bottle Bright, a fizzy cleaning tablet. Whatever approach you use, make sure you rinse the system several times and allow it to dry fully.