Grayl UltraPress Review: A Press-Style Water Purifier Bottle for Backcountry Days

Made by Grayl: See the Grayl UltraPress Water Purifier on grayl.com

The Grayl UltraPress is a 16.9 oz press-style water purifier bottle: you fill the outer cup from a stream, press the inner cartridge down, and drink about ten seconds later. Grayl says it removes viruses, bacteria and protozoa. It suits anglers who drink from backcountry water. FFIP score: 8.9/10.

The FFIP Scorecard

Criterion	Weight	Score	Why
Performance	35	10	Easy, almost foolproof clean water, and hard to beat once you add durability.
Build quality	20	10	The bottles look great and work well, and the filters are easy to use and service.
Ease of setup/use	20	8	Insert a filter and start pressing; it takes some muscle, and newer products serve other needs.
Portability/packability	10	7	Indestructible and goes anywhere, but bulky and heavy.
Value	15	7	Expensive bottles and replacement filters, but in line with the competition.
Overall (weighted)	100	8.9

How Does the Grayl UltraPress Purify Water? The Science Behind the Press

Filtering versus purifying

Filtering removes particles you can trap physically: sediment, silt and microplastics, plus larger organisms like protozoan cysts. Purifying also removes or inactivates viruses, which are far smaller. Typical protozoan cysts such as Giardia run a few microns across, bacteria are roughly a few tenths of a micron to a few microns, and viruses are often below 0.3 microns. A filter that only sieves by pore size has to be extremely tight to stop viruses, and tight filters clog and press slowly.

Electroadsorption: the charge trick

Grayl says its cartridge contains non-woven ceramic fibers with a high electropositive charge. Many microorganisms carry a net negative charge on their surface in typical water, so they are drawn to and stuck on the positively charged fibers, even when the microbe is smaller than the gaps between fibers. Grayl calls this electroadsorption and says it traps submicron contaminants this way. Grayl does not publish a nominal pore size on the product page, so any pore-size number you read elsewhere is not from the maker.

Activated carbon: adsorption, not absorption

The cartridge also holds ultra-powdered activated carbon. Activated carbon is carbon processed to be riddled with microscopic pores, giving it an enormous internal surface area. Chemicals, pesticides, herbicides, heavy metals, VOCs and taste or odor compounds stick to that surface (adsorption) as water passes. Grayl lists PFAS and lead among the contaminants it filters and states the carbon improves taste, smell and clarity. Carbon works by contact time, which is why a fast press still has to push water through a dense bed.

The press mechanism

The inner press houses the cartridge and works like a piston. When you press it into the outer cup of dirty water, the water is forced up through the cartridge into the inner chamber that holds clean water. A one-way silicone valve stops water flowing back through the cartridge and allows drink mixes or electrolytes in the clean water. Grayl says this design keeps dirty water from touching the part you drink from, but you should still use the spout cap and wash the bottle if it contacts dirty water.

Cartridge life and what it will not do

Grayl rates the UltraPress cartridge for about 300 presses (150 L or 40 gallons), and tells you to replace it when press time reaches about 25 seconds or after three years from first use. It also says to avoid salty or brackish water, and that the carbon is not designed for industrial disasters, coal ash spills, high lead levels, mercury, nuclear disasters, high tannin concentrations or water with toxic blue-green algae. To extend life, start with the clearest water, and pre-strain silt through a handkerchief.

UltraPress or GeoPress?

The photo shows an UltraPress; the bottle is printed with the name. The GeoPress is the larger 24 oz version. Details are in the comparison below.

On the Water with the Grayl UltraPress Water Purifier

I use my Grayl UltraPress all the time, both around camp and on fishing days. The best part is that I no longer have to haul large amounts of water. I carry the bottle, find a stream or lake, and press my way to clean water.

Pressing takes some muscle, and that is true no matter which size you buy. It takes the same effort to press the small bottle as the big one, so size comes down to where you are using it. A bigger bottle is nice on a boat; for a day on the water you may want something smaller.

Water is the supply line on any backcountry day. If you fish remote water on your own, read our guide to solo backcountry fly fishing and our first fly fishing trip plan for the rest of the checklist.

How Does the Grayl UltraPress Score, Criterion by Criterion?

Performance (Score: 10/10)

Performance is how fast and how safe. Grayl lists a flow of 10 seconds per 16.9 oz (3 liters per minute), and states removal of 99.99% of viruses, 99.9999% of bacteria and 99.9% of protozoan cysts. It also says the cartridge meets or exceeds NSF/ANSI protocols 42 and 53 in independent lab testing and meets the EPA Guide Standard and Protocol for microbiological purifiers. Those are the maker's claims, so read them as such. On the bank, ten seconds per press is the number that decides whether you actually drink when you are thirsty. If you need clean water and want something easy and almost foolproof, I think this is a great choice, and between that and durability it is hard to beat.

Build quality (Score: 10/10)

The UltraPress body is made from BPA-free polypropylene #5, food-grade silicone, TPE and ABS, with TopoGrip TPE on the heavy-use surfaces. Grayl states it withstands 6 ft drops when full of water onto concrete and backs the bottle with a 10-year warranty on workmanship and materials. The cartridge is made in the United States and the bottle in China, per the maker. The bottles look great and function well, the bottle is close to indestructible, and the filters are easy to use and service when needed.

Ease of setup/use (Score: 8/10)

There is nothing to assemble. You pull the inner press out of the outer cup, fill the cup with dirty water to the max fill line, twist the SimpleVent cap a half turn to vent air, and press down steadily with your body weight. Grayl says dirty water never enters the inner press, which holds the clean water you drink. Pressing gets slower as the cartridge wears, and cold water presses harder, which Grayl says does not necessarily mean the cartridge is spent. I use mine around camp and on fishing days, and pressing takes some muscle. Other products have come out that serve different purposes and could be a better option for you.

Portability/packability (Score: 7/10)

The UltraPress weighs 12.5 oz (354 g), stands 9.75 in tall and about 2.95 in across at the base, so it fits a cup holder and most side pockets. The bottle is indestructible and can go anywhere, but it is a bit bulky and heavy. It can clip to a pack or be strapped in, though it takes a little more space than other options. Grayl suggests carrying it empty and filling at the source rather than hauling water, and I like not carrying large amounts of water. You do need a water source within reach.

Value (Score: 7/10)

At $89.95 plus replacement cartridges at $24.95 each (per maker pricing at the time of writing), the cost per liter over a 150 L cartridge is low compared with bottled water. The bottles are expensive and you do have to replace filters, but they last a long time, and I think the price sits right up there with the rest of the category. The 24 oz GeoPress is the larger sibling and lists a longer cartridge life, so volume users should weigh that.

Who Should Buy the Grayl UltraPress Water Purifier (and Who Should Skip It)?

Choose the UltraPress if you hike to remote water, camp from a truck or raft with unknown sources, or travel and want protection against viruses as well as bacteria and protozoa. It is a one-hand, no-wait tool that fits in a pack pocket. For planning a whole kit around it, our article on organizing for your next trip helps.

Skip it if you need to purify water for a group or for camp cooking, where a gravity system or a bigger bottle suits better, or if your only source is salty or brackish water. Always start with the clearest, moving water you can find.

How Does the UltraPress Compare to the Grayl GeoPress?

These figures come from Grayl's own pages at the time of writing.

Feature	UltraPress	GeoPress (Nature)
Capacity	16.9 oz (500 ml)	24 oz
Cartridge life	About 300 presses (150 L / 40 gal)	About 350 presses (250 L / 65 gal)
Price (per maker)	$89.95	$99.95

The UltraPress is smaller and fits cup holders and small pockets. The GeoPress carries more per press and has a longer-lived cartridge. If you are choosing between sizes, keep in mind that pressing takes the same effort regardless of size. The bigger bottle is nice on a boat, and for a day on the water you may want the smaller one.

Frequently Asked Questions

Does the Grayl UltraPress remove viruses?

Grayl says yes. It lists removal of 99.99% of viruses (such as rotavirus, hepatitis A and norovirus), 99.9999% of bacteria and 99.9% of protozoan cysts, and says the cartridge meets the EPA Guide Standard and Protocol for microbiological purifiers.

How long does a Grayl UltraPress cartridge last?

Grayl rates the cartridge for about 300 presses (150 liters or 40 gallons) and recommends replacing it when press time reaches about 25 seconds or three years after first use. An unopened cartridge has a 10-year shelf life.

What is the difference between the UltraPress and the GeoPress?

The UltraPress holds 16.9 oz and is rated for about 300 presses. The GeoPress holds 24 oz and Grayl rates its cartridge for about 350 presses (250 liters). The UltraPress is more compact; the GeoPress delivers more per press.

Can the Grayl purify salt water?

No. Grayl says to avoid salty or brackish water. Activated carbon and electroadsorption do not remove dissolved salts.

How does electroadsorption work in a water purifier?

Grayl's cartridge uses ceramic fibers with a strong positive charge. Microorganisms typically carry a negative surface charge, so they stick to the fibers as water passes, even if they are smaller than the gaps in the material.

Final Verdict

If you want a long-lasting purifier that is easy to use and durable, the Grayl UltraPress is a great option. It is priced in line with its competitors, the bottle is close to indestructible, and not hauling large amounts of water is a real perk. Expect to replace filters and to put some muscle into the press.

Christian's Pro Tip: Choose your size by where you will use it. Pressing takes the same effort whether the bottle is big or small, so go bigger for a boat and smaller for a day on the water.

Tight lines, everyone!