The Grayl UltraPress Water Purifier (16.9 fluid oz) is a convenient bottle-based water treatment solution designed to remove viruses, bacteria, protozoa, chemicals, and heavy metals from backcountry or frontcountry water sources. Unlike other water filters and treatment methods, the Grayl UltraPress does not require batteries, ultraviolet light bulbs, hoses, straws, pumping, sucking, or waiting for a chemical reaction to complete. It also doesn’t require carrying an extra reservoir or container to drink from and fits into bicycle bottle cages and automobile cup holders, extending its utility to other venues other than hiking trails.
Specs at a Glance
- Weight: 12.5 oz (357 g)
- Capacity: 16.9 oz (500 ml)
- Flow Rate: 10 seconds per 16.9 oz (3 liters/minute)
- UltraPress Purifier Cartridge Lifespan: 300 uses (150 liters / 40 gallons)
- Active Technology: Electroadsorption, ultra-powdered activated carbon, and silver treated zeolites
- Antimicrobial: Yes
- Chemical-free: Yes
- BPA free materials: Yes
- Removes 99.99% of viruses (e.g. Rotavirus, Hepatitis A)
- Removes 99.9999% of bacteria (e.g. E Coli, Salmonella)
- Removes 99.99% of protozoan cysts (e.g. Giardia, Cryptosporidium)
- Filters particulates (e.g. silt, microplastics), many chemicals (e.g. chlorine, benzene), and heavy metals (e.g. lead, arsenic)
How to Use the UltraPress
The Grayl UltraPress works like a French coffee press with an outer bottle and a plunger that fits inside it with a purifier element at the end. You fill the outer bottle with water from a stream or lake, insert the plunger/purifier element into it and press down.
This forces the water in the outer bottle through the filter and into the plunger’s interior, which holds the purified water and doubles as a 16.9 oz. bottle that you can drink from directly. It has a screw-on cap, so you have the option of carrying the clean water with you if you don’t want to drink it all up on the spot. Another option is to pour the purified water out of the Ultrapress and into a larger bottle or reservoir if you want to carry more at once.
Purifying 16.9 ounces of water takes 10 seconds and simply requires pushing the “plunger” into the outer bottle containing the dirty water. The best way to do this is to set the Grayl UltraPress on the ground, unscrew the top cap a 1/2 turn to vent displaced air, and push down on the plunger using your body weight. If you forget to unscrew the cap that half turn, it will become apparent because it will take more force to push the “plunger” down. You can reseal the cap when finished if you don’t want to consume the water right away.
To pull the plunger (inner bottle) out of the outer bottle, pull on the handle on top. That’s the easiest way to get it out. If it sticks, due to suction, just persist. It’s not actually stuck and will come out.
How it Works
The UltraPress purifier cartridge uses a technology called electro-adsorption, where relatively large pores are overlaid with a positively-charged mesh that latches onto germs like little magnets. The larger pore size is easier to force water through, unlike other popular hollow-fiber filters (Sawyer Squeeze or Katadyn BeFree), where you have to squeeze like mad to try to force water through the filter.
To purify water, you push the inner bottle (which has the purifier cartridge attached to the bottom) into the outer bottle containing dirty water. Clean water collects in the inner bottle, once it’s been passed through the cartridge. Once the inner bottle and purifier cartridge hit the bottom of the outer bottle, simply unscrew the cap on the inner bottle and drink the water or pour it into another container.
Purification vs Filtration
The Grayl UltraPress is called a “water purifier” because it removes more substances than a “water filter”, including chemicals such as chlorine and iodine, and heavy metals including lead and arsenic. Regular water filters don’t remove these. The UltraPress also removes viruses, making it an excellent solution for road trips and international travel, basically anywhere where they’re sketchy water or water that you’re unsure of.
However, the UltraPress is NOT designed to protect against industrial disasters, coal ash spills, very high lead levels, mercury, nuclear disasters, high tannin concentrations, or water that contains toxic blue-green algae (cyanobacteria). In these conditions, it’s important to find another water source.
Unlike most water filters or purifiers, the Grayl UltraPress can be accidentally frozen and withstand up to three (3) freeze/thaw cycles. Beyond three cycles, purifier performance begins to diminish and the manufacturer recommends that the purifier cartridge be replaced. Still, that’s a handy feature in case you happen to get caught out in the cold unexpectedly, especially in early spring or late autumn.
The UltraPress purification element is rated for 300 uses (150 liters / 40 gallons), making it a better solution for occasional use on day hikes, mountain bike rides, and fishing trips, rather than extended backpacking trips and thru-hikes. The cost of an UltraPress replacement purifier cartridge is $24.95.
Over time, the speed of purification will slow as the purification cartridge fills with impurities. When it takes 25 seconds to process 16.9 oz of water instead of the original 10 seconds, Grayl recommends replacing the purification cartridge. The cartridge will still work beyond this point, but processing times will increase.
Stored under proper conditions, an unopened Purifier Cartridge has a shelf life of 10 years. After a cartridge has been used, it lasts at least 3 additional years. if you only use the purifier occasionally, it’s best to let the cartridge dry out for 3-4 days before putting it away. Grayl has complete instructions for this on their website, but it’s pretty effortless.
The Grayl UltraPress Water Purifier is an innovative water treatment system that provides excellent protection against biological, chemical, and mineral contaminants, but is just as useful in more civilized or international settings to make your water safer to drink and taste better. I love the fact that it’s completely self-contained and includes an integrated cup and bottle which makes it super easy to pack and carry, without having to deal with extra hoses, reservoirs, bottles, batteries, straws, and wet floppy things on short hikes when there’s plenty of water around and you don’t need to carry much extra.
While you could use the UltraPress for backpacking to purify more than 16.9 oz (a half-liter) of water at a time to carry, the purifier cartridge’s limited lifespan of 150 liters, the cost of replacement cartridges, and the time needed to process larger quantities of water make it a less desirable solution for long-distance backpacking or group trips. Still, I’m impressed by the ingenuity and ease of use of the Grayl UltraPress and think it’s an excellent water treatment solution, especially for hikers and outdoors people in the backcountry, as well as more urban environments, where the need to purify your water probably is even greater.
Disclosure: Grayl donated an UtraPress for this reviewSectionHiker is reader-supported. We independently research, test, and rate the best products. We only make money if you purchase a product through our affiliate links. Help us continue to test and write unsponsored and independent gear reviews, beginner FAQs, and free hiking guides.