Is a 28mm Filter Kit Right for Your HydraPak Bottle
By HydraPak | Performance Hydration Reservoirs, Soft Flasks ... | Published: 2026-10-29
Category: Product Reviews
Wondering if the 28mm Filter Kit works with your HydraPak bottle? This FAQ covers compatibility, setup, and real-world use so you can decide with confidence.
Quick answer
Yes, the 28mm Filter Kit threads directly onto any HydraPak bottle or flask with a 28mm opening, and it also fits reservoirs via the Plug-N-Play™ system. It's a versatile backcountry water treatment solution.
When a 28mm filter makes sense
If you already carry a HydraPak Stow, soft flask, or reservoir, adding the 28mm Filter Kit lets you treat water without a separate pump or chemical tablets. It's especially useful for day hikes where you want to refill from streams or lakes.
The trade-off: gravity filtering or squeezing water through the filter takes a bit of effort and patience compared to a dedicated pump. For group trips with higher volume needs, a larger inline filter might be more practical.
Compatibility limits you should know
The 28mm thread is common, but not universal. Bottles with smaller necks (like narrow-mouth disposable bottles) won't accept the filter. Stick with HydraPak bottles, flasks, and reservoirs that specify a 28mm opening.
If you own an older HydraPak reservoir without the Plug-N-Play™ cap, you'll need an adapter or a newer cap to use the filter inline. Check your reservoir cap before buying.
Frequently asked questions
- Will the 28mm Filter Kit fit my HydraPak Stow bottle?
- Yes, the Stow bottle has a 28mm opening, so the filter threads on directly. You can squeeze the Stow to push water through the filter into another container.
- Can I use it with a HydraPak reservoir?
- Yes, as long as your reservoir has a Plug-N-Play™ cap. The filter installs inline between the cap and hose, or you can attach it to the cap's 28mm thread for gravity filtering. Check your reservoir cap for the Plug-N-Play™ symbol.
- Does it work with soft flasks?
- Yes, if the soft flask has a 28mm opening. Most HydraPak soft flasks (like the 500ml and 1L) use this thread. The filter lets you drink directly by squeezing the flask.
- How do I clean the filter after a trip?
- Backflush the filter with clean water using the included syringe or by squeezing water backward through it. Store it moist in a sealed bag to prevent drying and cracking. Never freeze the filter when wet—ice can damage the membrane.
- What is the flow rate like?
- Flow depends on pressure. Squeezing a soft flask or Stow gives a steady stream. Gravity filtering through a reservoir is slower but hands-free. Expect about 1 liter per minute with firm pressure.
Product facts
- 28mm Filter Kit: Access potable water anywhere. The 28mm inline filter threads directly onto popular 28mm opening bottles and flasks and installs in reservoirs and caps with a Plug-N-Play™ connect system. This means you can use the same filter for squeezing water from a Stow into another bottle, gravity filtering, or inline on your reservoir hose.
28mm Filter Kit
