The Grayl GeoPress Water Purifier is a bottle-based water filter that removes bacteria, viruses, and protozoa from contaminated backcountry and international water sources. It's easy to use, portable, and safe for individuals to use for day hiking, fishing, or international travel, especially when you don't want to deal with a more complicated hose, bladder, or pump-based water purifier. The Geopress also addresses cross-contamination, which happens when you accidentally re-contaminate the drinking vessel or water you've just purified.

• Removes: Protozoa, Bacteria, and Viruses
• GeoPress purifies and filters 24 fl. oz. of water in 8 sec.
• The purifier's (replaceable) cartridge is rated for 350 cycles (65 gal./250L) or 3 years have elapsed since first use
• Meets the EPA guide standard and protocol for testing microbiological water purifiers
• Filter medium: Electroabsorption/activated carbon
• Dry weight: 15.9 oz
• 10.4 x 5.6 x 3.4 inches

The GeoPress has an outer and inner bottle (top photo), with a filter at one end and a screw-on drinking spout at the other. To use it, pull the inner bottle out of the outer bottle, fill it with suspect water, then push the inner bottle into the outer bottle like a French press. It takes some elbow grease (force) to push the inner bottle down, but doing so forces water through the purifier's filter element, filling the inner bottle with purified water. To drink it, unscrew the cap at the top and sip. It's that easy.

Depending on water quality, the purifier's filter element lasts for about 350 uses. When new, it takes about 8 seconds to push the inner bottle with its attached purifier filter into the full outer bottle, containing suspect water. When the amount of time to perform this action takes longer than 35 seconds, you know it's time to change the purifier filter, which unscrews with a twist of the wrist. Replacement purifier filter elements are sold separately for about 30 bucks each.

You then press the inner “clean” bottle with the filter at the bottom forcefully into the container of “dirty water

When filtering,  you can loosen the top cap a 1/2 turn to let the air out of the inner bottle and make the pressing motion a little easier.

Once purified, clean water fills the inner bottle. You have the option to drink it immediately, carry it as you would with any water bottle, pour it into a separate bottle if you prefer to carry it that way, or share it with others.

Cross-contamination

Cross-contamination occurs when you accidentally contaminate the part of your purifier or filter system that you drink from. This can occur if you touch a drinking spout with wet hands from contaminated water or if the mouthpiece of your hydration bladder drops in the dirt. The only way to decontaminate the drinking spout is to sterilize it by washing it with chlorinated water. Cross-contamination is one of the key reasons people still get sick on hikes, even when they use a water filter or water purifier.

The Grayl GeoPress guards against cross-contamination because it has a screw top that covers the drinking spout. As long as you keep that drinking spout away from unpurified water, you can safely drink from it or pour the bottle's contents into other containers for consumption.

The screw-on cap prevents unpurified “dirty water” from contaminating the end you drink from.

Recommendation

The Grayl GeoPress is a bottle-based water filter and purifier that's ideal for removing bacteria, viruses, and protozoa from backcountry or international water sources. Weighing 15.9 ounces dry, it's too low volume for general-purpose backpacking, where you probably want to process several liters of water at a time (since it can only purify 24 ounces at once). Instead, I've found it to be a great water treatment solution for outdoor recreational activities like day hiking or fishing, where there's plenty of water around, so you don't have to carry any, and you can drink when you're thirsty.  The GeoPress is also simple enough for anyone to use casually without a lot of training, making it a valuable general-purpose solution for all your family members.

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