HydraPak Ultraflask+ 42mm Filter Cap

HydraPak UltraFlask+ 42mm Filter Cap – Lightweight Water Filtration for Trail Running

Run further. Carry less. Filter on the move.

Stay hydrated on your longest adventures with the HydraPak UltraFlask+ 42mm Filter Cap, an ultralight water filtration system designed specifically for trail runners, ultra-marathon athletes and fastpackers.

Weighing just 36 grams, this compact filter cap transforms compatible HydraPak 42mm running flasks and handheld bottles into convenient water filtration systems, allowing you to drink filtered freshwater directly through the integrated high-flow Blaster™ bite valve.

Featuring advanced hollow-fibre filtration technology, the UltraFlask+ Filter Cap effectively removes common waterborne bacteria and parasitic cysts, making it a practical solution for adventures where suitable freshwater sources are available.

With a filtration capacity of approximately 1,500 litres and a flow rate exceeding 1 litre per minute, it's designed to deliver convenient hydration without slowing you down.

Whether you're tackling a remote trail, exploring the Perth Hills, hiking the Bibbulmun Track or preparing for your next ultra-distance adventure, the HydraPak UltraFlask+ Filter Cap helps you manage your water supply without carrying unnecessary weight.

Minimal weight. Maximum convenience. More freedom to explore.

Key Features

• Ultralight 36g Design: Minimal weight and bulk for trail running, ultra-marathons and fastpacking.

• Integrated Hollow-Fibre Water Filter: Removes common waterborne bacteria and parasitic cysts from suitable freshwater sources.

• 42mm Thread Compatibility: Fits HydraPak running flasks and handheld bottles with compatible 42mm openings.

• High-Flow Blaster™ Bite Valve: Allows you to drink filtered water directly from your flask.

• Auto-Sealing Bite Valve: Closes after each sip to help prevent unwanted drips.

• Up to 1,500L Filtration Capacity: Designed for extended use when properly maintained.

• Fast Filtration: Flow rate greater than 1 litre per minute under specified conditions.

• Included Backflush Adapter: Makes it possible to clean the filter and help restore flow rate.

• Compact, Running-Focused Design: Fits into your existing hydration setup without requiring a separate filtration bottle.

Why Choose the HydraPak UltraFlask+ Filter Cap?

When you're running long distances, every gram matters.

Carrying additional water can significantly increase the weight of your running vest or pack, particularly during ultra-marathons and remote trail adventures.

The HydraPak UltraFlask+ 42mm Filter Cap provides a practical alternative when reliable freshwater sources are available along your route.

Instead of carrying all your water from the start, you can refill a compatible flask and filter water as you drink.

Unlike larger water filtration systems designed primarily for camping, the UltraFlask+ Filter Cap is purpose-built for runners, combining a lightweight filter with a familiar bite-valve drinking system.

Its compact construction and convenient design make it especially appealing to runners who want to simplify their equipment without sacrificing essential functionality.

Filtration Performance

The HydraPak UltraFlask+ Filter Cap uses hollow-fibre filtration technology to reduce common freshwater pathogens.

Manufacturer-stated filtration performance:

• 99.999% reduction of common waterborne bacteria, including E. coli.

• 99.9999% reduction of parasitic cysts, including Giardia and Cryptosporidium.

• Approximately 1,500 litres of filtration capacity.

• Greater than 1 litre per minute filtration flow rate.

These figures apply under the manufacturer's specified testing conditions.

Best For

• Trail Running: Lightweight filtration for routes with suitable freshwater access.

• Ultra-Marathons: Convenient hydration for long-distance training and unsupported adventures.

• Fastpacking: A compact filtration solution for weight-conscious multi-day trips.

• Hiking & Bushwalking: Practical water filtration for remote trails and extended adventures.

• Mountain Running: Minimalist hydration equipment for demanding terrain.

• Adventure Racing: Compact filtration for events where permitted.

• Bikepacking: Lightweight water filtration for extended outdoor journeys.

How to Use the HydraPak UltraFlask+ Filter Cap

1. Fill your compatible flask: Collect water from a suitable freshwater source.

2. Attach the filter cap: Screw the UltraFlask+ Filter Cap securely onto your HydraPak 42mm flask.

3. Drink through the Blaster™ valve: Squeeze the flask and drink through the integrated filter system.

4. Clean when required: Use the included backflush adapter according to HydraPak's instructions to help restore flow.

5. Store correctly: Follow the manufacturer's cleaning, drying and storage guidance to protect the filter.

Tribe&Trail Tip: Always plan your water sources before heading into remote terrain. Seasonal creeks and streams in Western Australia can be unreliable, particularly during warmer months. Carry sufficient water between dependable refill points.

UltraFlask+ Filter Cap vs HydraPak 42mm Filter Cap

HydraPak offers two filtration caps designed for different outdoor applications.

UltraFlask+ 42mm Filter Cap

• Weighs just 36g.

• Features a high-flow Blaster™ bite valve.

• Designed specifically for running flasks and handheld hydration.

• Ideal for trail running, ultra-marathons and fastpacking.

HydraPak 42mm Filter Cap

• Weighs 57g.

• Features a high-flow drinking nozzle with dust cover.

• Designed for a broader range of compatible HydraPak water storage products.

• Ideal for hiking, camping and general outdoor filtration.

For runners who prefer drinking directly from a soft flask through a bite valve, the UltraFlask+ Filter Cap is the more running-focused option.

Important Water Filtration Considerations

The UltraFlask+ Filter Cap is designed to reduce specified bacteria and parasitic cysts from freshwater.

It is not a complete water purification system and should not be relied upon to remove viruses, dissolved chemicals, heavy metals or harmful algal toxins.

Avoid collecting water from sources affected by agricultural runoff, industrial contamination or visible algal blooms.

The hollow-fibre membrane can also be damaged by freezing. Protect the filter from freezing temperatures and follow the manufacturer's maintenance instructions.

Why Tribe&Trail?

At Tribe&Trail, we understand the importance of carrying reliable hydration equipment without unnecessary weight.

As Western Australia's dedicated Run | Hike | Walk store, we carefully select technical hydration systems, running equipment and outdoor essentials to help you prepare for every adventure.

Whether you're exploring the Perth Hills, preparing for Transcend Ultra, tackling an unsupported long-distance run or hiking the Bibbulmun Track, our experienced team can help you choose the right hydration setup.

Visit our Leederville store for practical advice on HydraPak soft flasks, running vests, water filtration and endurance equipment.

Run | Hike | Walk — For Every Trail.