This photo shows the GRAYL GEOPRESS Purifier and GRAYL ULTRALIGHT Purifier next to a creek.

GRAYL GEOPRESS Purifier Review: ‘Filters Out Viruses!’

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The GRAYL GEOPRESS Purifier is an all-in-one water bottle filter and purifier that turns sketchy water into safe drinking water. In addition to filtering out bacteria and protozoan cysts, it filters out viruses, too. That’s very cool.

To get us a closer look, GRAYL sent Man Makes Fire two GRAYL review units. This is what we learned:

GRAYL GEOPRESS Purifier Review

Here’s the short review: Get a GRAYL water purifier right now because every household should have one. You can take it hiking, take it camping, keep it in your vehicle, or use it when a natural disaster messes up your municipal water supply. That’s the short review.

This photo shows the GRAYL GEOPRESS Purifier and GRAYL ULTRALIGHT Purifier on the bank of a creek.
The GRAYL GEOPRESS and ULTRALIGHT Compact water purifiers blend a water bottle design with a super-effective filtration system.

Here’s the long review: GRAYL was born from outdoor adventurers and international travelers who wanted to create an easy-to-use water filter system that would be safe for risky water sources all over the world — even water with viruses, which most water filters can’t eliminate.

While backcountry water sources in the United States and Canada are usually not home to viruses, many water sources in developing nations do have waterborne viruses. Even water from some international hotels can harbor viruses within their water systems.

If you’re going to travel to less developed areas of the world that also have problems with viruses in water — including plenty of bacteria and protozoa that can make you sick — you need a high-quality water purifier. In addition, we believe that most people should have some sort of water filter for emergency purposes — as well as for camping, hiking, backpacking, and hunting.

This photo shows the GRAYL ULTRALIGHT Purifier taken apart.
The GRAYL purifier system uses one cup for dirty water (left) and a second cup with a filter attached (right) as a press to force the water through the filter and into the bottle. It works well.

The GRAYL GEOPRESS and ULTRALIGHT Compact water bottle purifiers are a great option for emergencies, backcountry hiking and backpacking, as well as for international travel. They’re easy to use. They don’t need batteries or UV light. They’re durable. They’re very packable and provide you with a storage vessel you can drink from on the go.

How Do GRAYL Purifiers Filter Bad Water?

GRAYL water purifiers have an external cup, which is a lot like a sleeve. GRAYL calls it the Outer Refill. The purifiers also have a bottle that fits tightly inside of the Outer Refill. GRAYL calls the bottle the Inner Press. At the bottom of the Inner Press is a purifier cartridge.

The Outer Refill (external cup) is for dirty water. To start the purifying process, you fill the external cup with dirty water to the maximum fill line. Next, you place the bottom of the clean water bottle over the cup of dirty water. You then push down on the top of the bottle, a.k.a. the Inner Press, and this action forces the dirty water through the filter and into the bottle section, cleaning the water as it goes.

It takes about 8-15 seconds.

So, then, how does the GRAYL purifier cartridge work?

The purifier cartridge uses non-woven ceramic fibers to block particulates — think sediment and microplastics. In addition, GRAYL has added positively charged ions and powdered activated carbon. When you force dirty water through the filter, GRAYL says the ion exchange permanently binds viruses, protozoa, and bacteria. The activated carbon absorbs chemicals, heavy metals, and odors.

How to Press the GRAYL Purifiers

The GRAYL purification process takes a bit of pressure and most importantly, technique. The easiest way is to place the Outer Refill on a stable surface on the ground or below your waist on a rock, bench, or chair. By having the Outer Refill low, you can simply use your upper body weight to provide the force needed to press the dirty water.

Next, you want to make sure that you loosen the cap on the ULTRALIGHT Compact version to allow air to escape. (If you don’t loosen the cap, you’ll be compressing the air inside the bottle, which will make it hard to completely press.) On the GEOPRESS version, you can tighten the lid but loosen the drinking spout cap a half turn.

Place the heels of both hands on the outer edge of the Inner Press and push down slowly, using your body weight. That’s it. It’s that simple.

This photo shows a man drinking from a GRAYL GEOPRESS Purifier.
Works great!

The larger 24-ounce GEOPRESS will handle about 350 presses, delivering 24 ounces of water each time. This equates to about 65 gallons of purified, safe drinking water.

The smaller 16-ounce ULTRALIGHT Compact will handle about 300 presses of 16 ounces of water, which equates to about 40 gallons of purified water.

Cartridge lifespan depends on the amount of sediment in the water — very dirty water could shorten the lifespan of your cartridge.

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You’re likely wondering which GRAYL purifier should I buy?

The most obvious difference is the water bottle capacity — 24 ounces vs 16 ounces. It’s a classic decision factor — weight, size and carrying capacity. Hold that thought for a moment.

The design of the two versions offers a few different benefits. Get the ULTRALIGHT Compact Purifier if you want a lightweight option for travel and easy packability. It offers a great blend of usability without taking up much space.

However, the benefits of the larger GEOPRESS Purifier might sway you. First, it has an handy drinking spout with its own small cap. I prefer drinking from a spout because it’s easier when you’re in a moving vehicle.

Second, the small cap lets you more easily vent the Inner Press as you purify water, making the process a bit easier as you learn the technique.

Third, the larger shape of the top lid makes it easier to press.

Fourth, the difference in the diameter of the filter cartridge allows you to press the water a bit faster. Despite being bigger, you can press 24 ounces in the GEOPRESS in as little as 8 seconds while the ULTRALIGHT takes 15 seconds to press 16 ounces. As both cartridges trap gunk over time, the flow rates will decrease (but the filter remains effective). When it takes 30-plus seconds to press filter your bottle, it’s time to replace your cartridge.

Best Use Cases

The most obvious use case is for international travelers to countries with less developed water supply systems that might also harbor waterborne pathogens. The GRAYL purifiers can filter out viruses, bacteria, and protozoan cysts, including Rotavirus, Hepatitis A, Norovirus, Giardiasis, Cryptosporidium, E. Coli, Cholera, Salmonella, Dysentery and more.

It also filters larger particulates like sediment and microplastics and even some chemicals, pesticides and heavy metals. There are other options that can kill viruses, like a UV light-based Katadyn Steripen. A Steripen is small but it requires batteries or a charge. Its effectiveness is lessened with murky water. The excellent MSR Guardian Purifier is arguably the best portable water filter/purifier, but it’s a bit bulky and isn’t as handy as a GRAYL option.

This photo shows the GRAYL GEOPRESS Purifier next to a replacement filter cartridge.
You can replace the filters when they wear out.

Aside from international travelers, GRAYL water bottle filters are great for emergencies. If your municipal water supply is ever compromised — which happens somewhere in the U.S. every year — you can ensure that your family can easily make safe drinking water. Depending on the level of disruption, this might be critically important.

For outdoor recreation, the GRAYL ease of use is fantastic. All you have to do is toss the bottle in your backpack and you’re good to go. You don’t have to remember to bring a separate water filter.

But a GRAYL is not just for hiking in the backcountry. I’ve been on many camping and fishing trips, often with friends and family, where I underestimated the amount of water we would want to drink. Sure, there might be plenty of soda and beer — and that is certainly important — but when you’re busy playing outside in the hot sun, everyone starts to crave water. If I’m the guy responsible for the health and thirst of other people off the grid, I take that seriously.

A GRAYL purifier can be your clean water backup.

Of course, you should know that for backpacking in the United States and Canada where waterborne viruses are not typically a problem, either GRAYL bottle size will certainly work, but they’re a bit heavy for serious backpackers who want to keep their carry weight down. Most U.S. and Canadian backpackers take dedicated lightweight water filters that, admittedly, don’t filter out viruses.

The Verdict: Outstanding

This review photo shows the GRAYL GEOPRESS Purifier in a close up of the inside of the bottle.
The GRAYL attention to detail is excellent.

The GRAYL GEOPRESS and ULTRALIGHT Compact Purifiers are awesome water filters with a unique and versatile design. The attention to detail is outstanding. You get rubberized bottoms for stability when pressing. You also get sweet color choices and the manufacturing quality is excellent throughout. The GEOPRESS cartridge even says “Purify Water Anywhere” on the inside where many people won’t even notice it.

If you’re heading to any international location that doesn’t have stellar water supplies, you should seriously consider taking the GRAYL ULTRALIGHT Compact Purifier with you. If you have family members traveling abroad, a GRAYL might make a great gift — which is how I first found GRAYL. I was looking for a simple purifier gift for a person traveling to Africa. As for me, I’ll keep a GRAYL in my pickup at all times. If you want an affordable and versatile water filtration system that can handle viruses, try a GRAYL. Very highly recommended.

Get the Gear:

Check shipping/pricing: Amazon | Moosejaw | OutdoorplayREI

Check shipping/pricing: AmazonMoosejaw | OutdoorplayREI

Cost effective
Easy to use
Ingenious all-in-one water bottle design is excellent
A bit heavy for North American backpackers (but definitely worth it for international travel)
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