Water is one of the heaviest items we carry, and any experienced hiker or backpacker can attest to this fact.

The U.S. Army recommends that an active individual consume approximately 75 percent of his or her body weight in ounces of water per day — about 112.5 fluid ounces for a 150-pound person, or even more under particularly hot or strenuous conditions. This amount of water weighs about 7.3 pounds; this doesn’t seem like much, but it belies an aspect that’s often overlooked: the space that water occupies.

Once you drink every drop, hard plastic or metal water bottles get lighter, but they don’t get any smaller. A 32-ounce canteen still occupies the same amount of space in your backpack, whether empty or full. Between refills, you’re hauling containers of air.

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The impracticality of this situation led to the development of collapsible water bottles. These soft-sided vessels expand when filled with liquid, and compress down to fit in small spaces when they’re not in use. They’re ideal for everything from everyday carry (EDC) to ultralight backpacking to action sports, and they can provide added water-carrying capacity when you need it most. Best of all, they keep the weight and bulk of your pack to an absolute minimum, so you can carry more of other items you need.

We obtained seven different collapsible bottles and tested each thoroughly. Read on to see which bottle came out on top.

CamelBak Quick Stow Chill Flask

Dimensions – Empty / Full
4.5 by 3.3 by 1.6 inches / 10.8 by 3.3 by 2 inches

Dry Weight
2 ounces

Capacity
14 fluid ounces (0.41 liter)

Body Material
Dual-layer bonded polyurethane with foam insulation

Dishwasher / Hot Liquid / Freezer Safe
No / No / Yes

Special Features
Chill foam insulation, Big Bite valve with lockout function

MSRP
$28

URL
www.camelbak.com

Notes
CamelBak is well known for its excellent hydration packs and reservoirs, and the company has expanded its 2017 lineup to include a new collapsible bottle. It’s known as the Quick Stow Flask, available in non-insulated and insulated Chill variants. We tested the latter model, which uses two layers of the same polyurethane material as full-size CamelBak reservoirs. Sandwiched between these layers is a thin sheet of Chill foam, which does a great job insulating the vessel. This is beneficial if you’re storing the reservoir in a pocket, as it repels body heat. Unfortunately, the added insulation also shrinks the capacity to 14 fluid ounces — barely larger than a can of soda. Aside from the borderline-impractical capacity, this is a strong contender.

Pros:

• Insulation keeps drinks ice cold, even on hot days.
• Bite valve makes drinking easy, lockout function stops leaks

Cons:

• All Quick Stow flasks are marketed as 500ml capacity, and the non-insulated version does match this specification. However, our insulated flask actually held only 415ml when filled to the brim.
• Not freestanding

Hydaway Large Collapsible Bottle

Dimensions – Empty / Full
1.3 inches tall, 4.3-inch diameter / 6 inches tall, 4.3-inch diameter

Dry Weight
5.7 ounces

Capacity
21 fluid ounces (0.6 liter)

Body Material
Food-grade silicone

Dishwasher / Hot Liquid / Freezer Safe
Yes (top rack) / Yes / Yes

Special Features
Carry handle, flip-up straw

MSRP
$20

URL
www.hydawaybottle.com

Notes
The Hydaway collapsible bottle was launched on Kickstarter by inventor and product designer Niki Singlaub. In his words, it’s intended to be “a durable, stable, fully functioning water bottle that collapses enough to fit in a back pocket.” We confirm that the flat disc-like structure of the Hydaway is ideal for back pockets ­­— it’s not much thicker than a full wallet, and the silicon rubber provides compressible give. To expand the bottle, just flip open the straw, then pull apart the lid and base like an accordion. After use, it’s easy to clean by placing in the dishwasher on the top rack. Unfortunately, it reminds us of a child’s sippy cup. If you can overlook the aesthetics, it’s an easy-to-use bottle with solid ergonomics and an affordable price.

Pros:

• Thin disc-shaped design fits comfortably into a pocket.
• Eight high-visibility color choices

Cons:

• Exterior appearance seems more kid-friendly than survival-oriented.

Hydrapak Stash 1L Collapsible Bottle

Dimensions – Empty / Full
2.3 inches tall, 4-inch diameter / 8.2 inches tall, 4-inch diameter

Dry Weight
3.2 ounces

Capacity
32 fluid ounces (1 liter)

Body Material
Thermoplastic polyurethane (TPU)

Dishwasher / Hot Liquid / Freezer Safe
No / Up to 140°F / Yes

Special Features
Carry handle, measurement markings

MSRP
$23

URL
www.hydrapak.com

Notes
The Hydrapak Stash is a 1-liter bottle that pairs thin and flexible 0.4mm film sides with a rigid neck and base. To expand, unscrew the cap and squeeze the midsection to pop open four radial tabs. The base then twists 180 degrees as it expands outward. This bottle’s industry-standard 63mm threads adapt to other caps, so you can easily add a straw, flip-top, or bite valve if you prefer. It also allows the attachment of water purifiers, such as the MSR Guardian featured in Issue 15. The thermoplastic polyurethane film sides seem quite durable and are backed by a lifetime guarantee against leaks, but they also proved difficult to grasp without squeezing. With a hard-sided bottle, we tend to grip the sides, but this bottle requires the user to hold it by the neck when uncapped. It’s also slightly tricky to clean thoroughly, due to crevices in the plastic base. Otherwise, the Stash is a compact bottle with a nice wide mouth and a lot of adaptability potential.

Pros:

• Standard 63mm wide mouth is compatible with many water filters, purifiers, and replacement caps.
• No-Leak lifetime guarantee provides peace of mind.

Cons:

• Soft sides can be tricky to grasp without compressing inward.
• Ridges in the base are difficult to thoroughly clean, although the wide mouth does make this easier.

Katadyn BeFree Filtration System

Dimensions – Empty / Full
4 by 2.8 by 2.4 inches / 9.3 by 2.8 by 2.4 inches

Dry Weight
2 ounces

Capacity
21 fluid ounces (0.6 liter)

Body Material
Thermoplastic polyurethane (TPU) produced by Hydrapak

Dishwasher / Hot Liquid / Freezer Safe
No / No / No

Special Features
Hollow fiber filter rated for up to 1,000L or 264-gallon lifespan, flip-top cap, measurement markings

MSRP
$40

URL
www.katadyn.com

Notes
Katadyn’s BeFree system is the result of a collaboration with Hydrapak. Hydrapak produces the flexible SoftFlask pouch, while Katadyn supplies the 42mm cap, flip-top drink nozzle, and hollow-fiber filter that purifies water as you drink. This integrated filter removes 99.9999 percent of bacteria and 99.9 percent of protozoa, meeting the NSF/ANSI P231 standard for water purification (see our water filter buyer’s guide in Issue 15 for more on this topic and why all those numbers after the decimal point matter). It also removes particulates and sediment, and retains an impressive 2-liters-per-minute flow rate. The filter can easily be cleaned by shaking or swishing in any fresh water source, or by backflushing with clean tap water. Aside from its ability to reduce the risk of waterborne illness, the BeFree system serves as an effective — albeit small — water container for active lifestyles. If your bug-out bag already contains a small canteen and a water filter, this could potentially replace both, while saving space and reducing pack weight.

Pros:

• Integrated water filter can help keep you hydrated and healthy.
• Cap and filter can be installed on any 42mm-mouth Hydrapak SoftFlask, with capacities ranging from 0.15L to 3L.

Cons:

• Larger-capacity SoftFlasks are available, but only sold separately by Hydrapak without the Katadyn filter. We wish there had been a few capacity options to choose from at the time of purchase.
• Not freestanding

Platypus PlusBottle

Dimensions – Empty / Full
3.6 by 6 by 1.2 inches / 11.8 by 4.5 by 3.2 inches

Dry Weight
1.3 ounces

Capacity
34 fluid ounces (1 liter)

Body Material
Polyurethane/polyethylene film

Dishwasher / Hot Liquid / Freezer Safe
Yes (top rack) / Yes / Yes

Special Features
Push-pull cap, carry loop, measurement markings, bacteria-resistant and mold-resistant silver-ion material

MSRP
$17

URL
www.cascadedesigns.com/platypus

Notes
The Platypus PlusBottle is a 1-liter reservoir constructed of flexible laminate, impregnated with a silver-ion material that’s said to resist mold and bacteria growth. (Silver has been used as a germ repellant for thousands of years.) The body feels pliable yet tough and can be packed flat or rolled up. The PlusBottle is available with your choice of either a screw-on cap or a push-pull cap. If you’re willing to spend an extra $13, an optional drink tube kit can turn this into a compact hydration bladder. The PlusBottle is also dishwasher- and freezer-safe, and it makes a great ice pack for hot days — just fill halfway and purge all air pockets inside before freezing. The narrow mouth isn’t ideal for cleaning, but it does conveniently adapt to standard vending machine bottle caps and threaded water filters. This bottle is great for the ultralight crowd, since it weighs next to nothing and occupies minimal space.

Pros:

• Ultra lightweight
• Made in the USA

Cons:

• Narrow mouth makes it difficult to thoroughly clean every nook and cranny
• Great for flat-packing, but won’t stay rolled-up unless you add rubber bands or a carabiner

Secur SP-1108 Solar Bottle Lantern

Dimensions – Empty / Full
3 inches tall, 3.8-inch diameter / 6.2 inches tall, 3.8-inch diameter

Dry Weight
8.7 ounces (including USB charging cable)

Capacity
25 fluid ounces (0.7 liter)

Body Material
Food-grade silicone

Dishwasher / Hot Liquid / Freezer Safe
No / Up to 140°F / No

Special Features
100-lumen waterproof LED light, integrated solar panel, magnetic USB charging cable, removable carry handle

MSRP
$30

URL
www.securproducts.com

Notes
The SP-1108 water bottle lantern is a brand-new release from Secur, and we got our hands on one of the first production models. In the past, we’ve lamented multi-functional products that are a jack-of-all-trades and master of none, but this bottle manages to add valuable features without compromising where it counts. Sure, it’s moderately heavier and larger than the other bottles here, but it manages to add a three-mode LED that’s surprisingly effective as a lantern or can be removed and hand-held as a flood light. The cap recharges via USB in three hours or via the built-in solar panel in 24 hours. The bottle itself is composed of silicone rubber and expands easily to hold 0.7 liter. The SP-1108 did produce an off-putting chemical odor when new, but this improved a bit with time. That said, we’d say this bottle would make a good multipurpose addition to a bug-out bag or emergency kit.

Pros:

• LED-lit cap can illuminate a whole room, runs for up to 12 hours, and recharges two ways
• Even without the extra features, it’s a very good collapsible bottle.

Cons:

• Bottle produces noticeable plastic odor and taste, although it dissipated somewhat after a few uses.
• Bulkier and heavier than other bottles here

Vapur Eclipse Blackout

Dimensions – Empty / Full
3.2 by 5.7 by 1.8 inches / 11.3 by 5.7 by 3 inches

Dry Weight
1.3 ounces

Capacity
34 fluid ounces (1 liter)

Body Material
Bonded three-ply (two outer nylon layers, inner layer of polyethylene)

Dishwasher / Hot Liquid / Freezer Safe
Yes (top rack) / Yes / Yes

Special Features
Flip-top SuperCap, integrated carabiner

MSRP
$14

URL
www.vapur.us

Notes
Eclipse Blackout sounds like it could be the title of a heavy metal album, but it’s actually the latest in Vapur’s line of “anti-bottles.” Appropriately, this 1-liter vessel is constructed of flexible three-ply material with a stealthy matte black finish. Cosmetics aside, the Eclipse packs almost completely flat or can roll into a compact bundle. When filled to the brim, the base expands and allows it to stand freely with minimal risk of tipping. A DrinkLink hydration tube has also been announced and will allow conversion of this bottle into a hydration reservoir by screwing on a new cap. The bottle’s integrated carabiner is one of our favorite features, since it provides a way to attach it to your belt loop or backpack, while keeping it from unrolling while stored. Even with the carabiner, the Eclipse barely nudges the scales at only 1.3 ounces. This “anti-bottle” is made in the USA, shipped and packaged with eco-friendly methods, and affordably priced — we had a hard time finding any major flaws while testing the Vapur.

Pros:

• Ultra-lightweight, but still manages to include a useful integrated carabiner
• Made in the USA

Cons:

• Vapur says the matte finish “will develop character resulting in a unique patina.” That’s a creative way of saying it will accumulate cosmetic scuffs — if you care about that sort of thing.

Written by Patrick McCarthy