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Grayl water filter: a press purifier that also lists virus removal

By the Plain Prepper editors. Updated 2026-10-15.

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Quick answer

A Grayl is a bottle you fill, then press: the inner cup pushes water through a cartridge in about 8 to 10 seconds. Grayl lists 99.99% of viruses, 99.9999% of bacteria and 99.9% of protozoan cysts removed, plus carbon for many chemicals. The 24 oz GeoPress cartridge lasts 350 presses (250 liters), and the 16.9 oz UltraPress lasts 300 presses (150 liters). Replace it when a press takes about 25 seconds, and never use it on salt water.

GeoPress, UltraPress and GeoPress Ti compared

Spec	GeoPress 24 oz	UltraPress 16.9 oz	GeoPress Ti 24 oz
Capacity	24 oz (710 ml)	16.9 oz (500 ml)	24 oz (710 ml)
Weight	15.9 oz	12.5 oz	20.125 oz
Press time	8 seconds (5 L/min)	10 seconds (3 L/min)	Up to 8 seconds (5 L/min)
Cartridge life	350 presses, 250 L (65 gal)	300 presses, 150 L (40 gal)	350 presses, 250 L (65 gal)
Drop rating	6 ft full, onto concrete	6 ft full, onto concrete	10 ft full, onto concrete
Extra	One-way drink mix valve	One-way valve pre-installed	Titanium cup doubles as a cook pot

All figures are from Grayl's product pages, checked October 2026.

What a Grayl removes

• Germs: Grayl lists 99.99% of viruses, 99.9999% of bacteria and 99.9% of protozoan cysts, naming Rotavirus, Hepatitis A, Norovirus, Giardia, Cryptosporidium, E. coli, cholera and Salmonella.
• Particles: silt, sediment and microplastics.
• Chemicals: Grayl says its ultra-powdered activated carbon adsorbs many chemicals, including PFAS and VOCs, plus pesticides, heavy metals, flavors and odors.
• How: Grayl describes non-woven ceramic fibers with a strong positive charge that trap microorganisms, a method it calls electroadsorption.
• Standards: Grayl lists certified-lab results meeting NSF/ANSI protocols 42 and 53 and the EPA Guide Standard and Protocol for microbiological water purifiers.

That virus claim is the main difference from many straw filters; CDC notes that a 0.3 micron filter removes bacteria and parasites but not viruses.

What a Grayl cannot fix

• Salt water: Grayl says to avoid salty or brackish water.
• Disaster chemistry: Grayl says it is not designed for industrial disasters, coal ash spills, high lead levels, mercury, nuclear disasters, high tannins, or toxic blue-green algae, and to find another source.
• Floodwater with chemicals: CDC warns that boiling or disinfecting cannot make water with harmful chemicals, toxins or radioactive material safe.
• Volume: one 250 liter cartridge is about 125 days of drinking water for one person at 2 liters a day, or about 31 days for a family of four; store water too, and see our emergency water storage guide.

Cartridge life and the 25 second rule

1. Watch the press time: Grayl says press time rises as the cartridge clogs; replace it at about 25 seconds, or three years after first use.
2. Cold water is slower: Grayl notes colder water may need a longer press and does not always mean the cartridge is done.
3. Protection continues: Grayl says the cartridge keeps protecting even as press time increases.
4. Dirty water shortens life: silt, sediment and tannins reduce lifespan; Grayl suggests prefiltering through a handkerchief or T-shirt.
5. Storage: Grayl lists a 10 year shelf life for an unopened, airtight cartridge, so a spare suits a kit.

The arithmetic checks out: 250 liters divided by 0.71 liters per fill is about 352 fills, close to the 350 presses Grayl lists.

How to use, clean and store a Grayl

• Fill: dip the outer cup into the cleanest water available, such as a stream rather than a stagnant pond.
• Press: push the inner press down through the filled outer cup; Grayl lists about 8 seconds for the GeoPress.
• Avoid cross-contamination: use the spout cap; if dirty water touches the inner press, Grayl says to wash the bottle parts (not the cartridge) with soapy water.
• After a trip: Grayl says to do a dry press, remove the cartridge and air-dry it for 2 to 4 days, hand wash the other parts, and store it assembled.
• Drink mixes: the one-way valve lets you add electrolytes after filtering, Grayl says.

Which Grayl for an emergency kit

• Most households: the GeoPress gives the most water per press and per cartridge.
• Small packs and car kits: the UltraPress is 3.4 oz lighter and slimmer, at 12.5 oz versus 15.9 oz.
• Cooking too: the GeoPress Ti's titanium cup works as a cook pot, so you can boil water in it when boiling is the safer choice.
• Spares: pack a sealed replacement cartridge; the unopened shelf life is 10 years.
• Compare options: see our LifeStraw and portable water filter guides for lighter filters without a virus claim.

What to look for when you buy

Questions people ask

Does a Grayl remove viruses?

Grayl lists 99.99% of viruses removed, along with 99.9999% of bacteria and 99.9% of protozoan cysts.

Can a Grayl filter salt water?

No; Grayl says to avoid salty or brackish water.

How long does a Grayl cartridge last?

Grayl lists 350 presses (250 L) for the GeoPress and 300 (150 L) for the UltraPress; replace at about 25 seconds per press or three years.

How do I clean a Grayl?

Grayl says to dry press, remove and air-dry the cartridge for 2 to 4 days, and hand wash the other parts with warm soapy water.

Sources

• 24oz GeoPress Purifier, GRAYL
• 16.9oz UltraPress Purifier, GRAYL
• 24oz GeoPress Ti Purifier, GRAYL
• GeoPress Purifier Cartridge, GRAYL
• About Water Treatment Options When Hiking, Camping, or Traveling, Centers for Disease Control and Prevention

Sources checked 2026-10-15.