Staying hydrated during outdoor adventures not only keeps you safe and healthy, it literally makes you feel better—you’ll enjoy your time outdoors more. Two tools that make getting the fluids you need easy and convenient: hydration reservoirs and hydration packs.

Hydration reservoirs, or bladders, are effective because they actually encourage you to drink frequently, since the hose is always at the ready—no stopping to dig out a water bottle. Their flat shape slips easily into a backpack, and unlike a water bottle, they get smaller as you drink. And the latest reservoirs are durable and leakproof. 

A hydration pack is any backpack (or one of its cousins, a vest or waist pack) designed to carry a reservoir, typically with an internal reservoir pocket and port for the hose to poke through. They range from small, sleek packs made for running and cycling to full-fledged daypacks big enough to handle all your hiking gear.

In this guide you’ll learn:

• How to choose the appropriate reservoir volume 
• Which reservoir features and closures to look for
• What reservoir accessories are available
• How to choose the right hydration pack size and style

Hydration Reservoirs

All reservoirs will tote your water efficiently, but they’re not all exactly alike. Consider these variables.

Volume

Reservoirs range from about 1.5 liters to 3 liters in capacity. The smallest ones hold enough water for a shorter day hike. If there are water sources available (and you carry a treatment device), you can save weight by carrying a smaller reservoir and refilling it as needed. Three-liter reservoirs are especially good for areas where water sources are scarce. When full, they’re considerably heavier (a 3-liter bladder holds about 6.5 pounds’ worth of water). 

Features

• Quick-connect hose: This allows you to easily detach the reservoir from its hose so you can refill it without having to remove and then re-thread the hose. 
• Leakproof bite valve: The bite valve is what you drink from, and some can be closed to prevent leaks. 
• Insulation: Reservoirs made for cold weather typically include insulation for both the bladder and hose to prevent freezing; it’s a nice feature for keeping water cold in hot weather, too.

Closure style

There are two main choices. 

• A screw-on closure seals like a jar lid; it’s secure, but sometimes can be difficult to thread and makes the reservoir harder to clean (a wide-mouth closure makes cleaning easier). 
• With a slide closure, you fold the top of the reservoir over and slide a clip on to hold it. This type lets you open the top wide for easier cleaning. 

Weight

Reservoirs don’t weigh much on their own, especially compared to the weight of the water they carry. But reservoir weights can vary by a few ounces—which might matter to dedicated ultralighters.

Accessories

• Drying rack: Reservoirs should be rinsed out and dried completely after each use, so a drying rack is helpful for propping yours open to dry. You can also improvise one out of a coat hanger. 
• Cleaning tools: Cleaning tablets and specialized brushes make it easier to give a reservoir a deep scrubbing. 
• Bite valve covers: These are great for keeping the mouthpiece clean, and are sometimes included. 
• Insulation: If your reservoir didn’t come with insulation (most don’t), you can buy an insulated pouch for use in cold and hot weather. 

Hydration Packs

If you need a reservoir plus a pack to haul it in, check out an all-in-one hydration pack. These come in a variety of sizes and styles.

Pack style

Backpacks: Many hydration packs are basically fully featured daypacks that come with an included reservoir. But others are designed specifically for biking or trail running: These packs tend to be smaller, lighter, and sleeker so that they don’t bounce around on your back or throw off your balance, and may have extra pockets on the front for easy access. Winter hydration packs usually come with insulation to keep water from freezing. 

Vests and waist packs: Fast-and-light explorers like trail runners and cyclists also favor a couple of backpack variations. Vests, which will hold a reservoir and/or water bottles and little else, fit close to the body with minimal bouncing. Waist packs are even smaller and lighter and hold a water bottle or reservoir on the small of your back. 

Volume 

• Under 10 liters: The smallest hydration packs fit a reservoir and a couple of other small items. They’re very light and streamlined, and ideal for day trips where you won’t need extra layers or lots of food. These are best for trail running and cycling, though you certainly could do shorter hikes with one, too. 
• 10 to 20 liters: These packs are still light, but can fit your water, a few layers, snacks, and essentials like a map and GPS. They’re great for more extended runs and rides as well as typical day hikes. 
• 25 to 35 liters: The largest hydration packs often have robust suspensions and full features for long days. They’re the heaviest models, and work best for hiking.

Features

• You can evaluate the features on a hydration pack, such as pockets and compression straps, much the same way you do a regular backpack. A couple of features do bear mentioning for hydration packs, though. 
• Clip or magnet: One of these on the pack’s straps holds the hose in place so you always know where it is and it’s easy to grab. 
• Hipbelt: Smaller hydration packs don’t always have a hipbelt. Hipbelts are great for distributing the weight of heavier loads and keeping the pack stable, but they might not be necessary on smaller packs that carry light loads and fit higher on your back. 

All articles are for general informational purposes.  Each individual’s needs, preferences, goals and abilities may vary.  Be sure to obtain all appropriate training, expert supervision and/or medical advice before engaging in strenuous or potentially hazardous activity.