HydraPak Flux Water Bottle Review

Bottom Line

Soft water bottles often take a back seat to their hard shell counterparts, but the packability and sturdy flexibility of the ultralight HydraPak Flux make it a top contender for travel and outdoor use. That’s why it made our list of the best water bottles. 

An excellent bottle with a uniquely durable and ergonomic design, the Flux kept us hydrated over dozens of miles hiking through Wyoming’s backcountry. We also found it a convenient carry to take along fly fishing. 

The HydraPak Flux is an ultralight bottle with longevity. Its soft body is incredibly durable, but it also has the ability to be contorted and compacted for packing or storage. It maintains these features all while weighing in as one of the lightest bottles we tested. The Flux has become one of our go-to favorites for hiking and backpacking, thanks to its light yet lasting design.

How We Tested

Gear analyst Marion Tucker researched 35 water bottles and tested the top 13 in the field while hiking and fly fishing in Wyoming. She conducted drop tests to evaluate their durability and ranked each bottle’s ergonomics, insulation, weight, and features after side-by-side comparisons.

Durability

Stainless steel water bottles have the best reputation for longevity, but the HydraPak’s long-term potential impressed us, despite being a soft shell plastic bottle. 

The Flux is made of burly yet flexible plastic – a robust material which proved resistant to tears and punctures and resilient against falls. We put the bottle through a series of tests, dropping it on a variety of surfaces: wood floors, sandy trails, and rocky cliff sides. Each time, the HydraPak bounced on impact, coming away without any indication that it had sustained a fall. Many bottles we reviewed suffered scuffs or scratches, but the HydraPak was unmarred by falls – even those onto jagged landings. 

The weakest element of the design is a side seam running the length of the bottle. This has the potential to deteriorate over time with repetitive folding and flexing. However, we’ve personally owned the Flux for a year, putting it through rough backcountry use over hundreds of miles backpacking. It remains in just as good of shape as when we first purchased it. 

The HydraPak’s flexible construction doesn’t come at the cost of structural integrity. The sturdiness of its materials prove adept at resisting damage from the most extreme use, setting the Flux apart from other soft bottles. It’s an ideal and potentially long-lasting choice for outdoor adventures.

Ergonomics

The HydraPak Flux is the contortionist of the water bottle world. Made of a malleable plastic that readily bends, folds, and compresses into whatever shape you need, the Flux is well suited for travel or squeezing it into the tight corners of a pack. 

When empty, the bottle can be collapsed into itself, neatly held in a compact shape by the built-in handle. This keeps it out of the way and saves space for storage. We’ve frequently brought the Flux with us fly fishing and love that it can be collapsed. In our experience it barely takes up any space when stashed in an already gear-laden shoulder pack while also being quick to remove for a fast refill along the river. 

Water is sipped via a nozzle that twists open and close for either fast-flow drinking or leak-free sealing. An attached, pivoting cover protects the mouthpiece from dirt and grime. The main lid can be fully removed to add ice and hydration mixes. The biggest detractor is the Flux’s initial plastic-y taste. It also takes multiple cleanings to rid the bottle of residual flavors. However, the Flux is dishwasher safe, making this task easier.

Insulation

As a non-insulated bottle, the HydraPak doesn’t maintain temperature control. However, unlike most plastic or soft shell bottles, it can hold both hot and cold water. 

The thin plastic construction of the Flux – though beneficial for its pliability – does not provide any help with temperature regulation. We found cold water became lukewarm in just under a couple hours and diminishing quicker in sunny conditions. 

One setback with hot liquid usage is temperature limitation. The Flux can only accept hot beverages up to 140 degrees Fahrenheit (60 degrees Celsius). With the boiling point of water much higher, it’s difficult to determine whether a drink is too hot for the HydraPak without a thermometer.  

Weight

Weighing only 3.6 ounces, the HydraPak Flux is an ultralight option that’s more environmentally friendly than some of its ounce-saving counterparts. 

We used the HydraPak in conjunction with a SmartWater bottle during a multi-day backpacking trip in Wyoming. Its light weight – along with its flexible and collapsible design -made it a comfortable carry. We hardly noticed it in our pack even after days on the trail. More durable than single-use bottles, the HydraPak is worth the extra ounce or two. If you’re trying to limit weight and single-use plastics, the Flux is a sustainable choice that keeps your pack as light as possible.

Features

Personalization isn’t a huge priority for HydraPak. The Flux is only offered in a few color choices and comes in 750mL and 1.5L sizes.

Features may not set the HydraPak apart from other brands, but we explored the bottle’s filter compatibility. Equipped with a 42mm threaded opening, the Flux can be used with HydraPak’s own Filter Cap – which removes bacteria, parasitic cysts, and microplastics – as well as the Katadyn BeFree Filter. 

Equipped with the filter cap, we’ve used this bottle on backpacking and fishing trips. Simply dipping the Flux into a nearby stream and taking a sip transforms surrounding water sources into immediate and worry-free spots to rehydrate. 

Should You Buy the HydraPak Flux Water Bottle?

The HydraPak Flux is a high value bottle at an incredibly low cost. One of the least expensive water bottles we reviewed, the HydraPak packs a punch with its innovative design that simultaneously offers extreme durability and uniquely flexible design. Filter compatibility gives this bottle an extra edge, making it an excellent ultralight choice that also makes water purification a breeze. Especially well-suited for backcountry use, this bottle is equipped to support you in all your adventures. TheFlux is a well-rounded pick that will last many years and meet your hydration needs with just a few ounces of pack weight.

What Other Water Bottles Should You Consider?

For a full list of recommendations, check out our guide to the Best Water Bottles. 

Hydro Flask Wide Mouth Review: Looking for a high-value water bottle that will also insulate your beverage? Built with stainless steel and double wall insulation, the Hydro Flask Wide Mouth is durable, stylish, and more environmentally friendly than a plastic bottle. 

Grayl GeoPress Review: Whether in the backcountry or traveling abroad, the Grayl GeoPress provides the most intensive water purification of any filtration capable bottle available, using an innovative press method to produce clean, good tasting water. 

Nalgene Wide Mouth Review: For backcountry adventures, look no further than the Nalgene Wide Mouth for a classic water bottle that’s built to withstand the most extreme conditions without blowing your budget.h Revi