Backpacking with the GRAYL GeoPress: The Good, the Bad & the Tannins

By: Becky Bucar

First Stop on the Adventure Bucket List: Ultralight Backpacking

As I approach my 50th birthday, I’m checking off big goals, starting with an ultralight backpacking trip. One of my biggest concerns was how to filter water safely and easily on the trail. After some research, I landed on the GRAYL GeoPress, and it felt like a game-changer… at first.

Why I Chose the GeoPress

The 24 oz GRAYL GeoPress caught my eye for a few reasons:

• It filters out viruses, bacteria, protozoa, pesticides, and microplastics, which is more thorough than many compact filters.

• It’s less complex than pump or squeeze-style systems, just fill, press, and drink.

• It has a rigid shape that stores easily in a side pocket.

• The chug spout makes sipping on the go super easy.

• And honestly, it just feels durable and travel-ready.

I plan to bring it on an upcoming trip to Brazil, where clean water isn’t always a given. Having something I can trust without relying on bottled water makes a huge difference.

Pros & (A Few) Cons

During my test run at Watson Lake, I loved how easy it was:

• Fill the outer cup with water

• Press the filter through

• Within seconds, clean, drinkable water

I filled my water bladder with it and kept extra in the container itself. It also handled electrolytes and powders well without clogging.

That said, I do wish it held a bit more water. While 24 oz is decent, a slightly larger capacity would mean fewer refill stops. (Though I get that anything bigger = more weight.)

Post-Trip Reality Check: A Clog in the Plan

Here’s where things took a turn. On my actual backpacking trip, the filter started getting harder to press. What once took seconds now took well over 25 seconds, the threshold GRAYL uses to signal that the cartridge is done.

Eventually, I had to call my husband to meet me at the trailhead with a different filter system. Not ideal.

I contacted GRAYL’s super helpful customer support, and they let me know the issue was likely due to tannins in the water, a common compound in lakes that gives the water a yellowish tint. Tannins clog the purifier media quickly, and they recommend avoiding any discolored sources altogether.

Still a Great Option (With a Caveat)

From GRAYL’s team:

“Repeated exposure will have a cumulative effect. Tannins have a high affinity for the purifier media…a limitation of our current tech, but one we are looking to get around with future revisions.”

So, while I won’t be relying on this for tannin-heavy lake water, I still love it for international travel or clear alpine streams. With an extra cartridge on hand, I’d be open to taking it back into the backcountry under the right conditions.