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Review: Grayl Ultralight Water Purifier Bottle

Water purifier bottle

A wonderfully simple, effective, lightweight water purification system that eliminates waterborne nasties and saves you time out on the trail.

If you’re on the hunt for a water purification system that’s light, takes up little pack space and is superbly reliable, you really don’t have to look any further than the Grayl Ultralight Purifier. This brilliantly practical little bottle is fast and easy to use. You fill it up, plunge the inner press and hey presto…you’ve got safe, clean drinking water!

The Grayl UP uses a purifying cartridge which works pretty much like the wire mesh in your standard coffee press. The difference is that the Grayl doesn’t simply keep out coffee-grind-like sediment, but uses electroadhesion and ion exchange to thwart just about any and every pathogen, virus, protozoa and bacteria type you could possibly imagine. For safe hydration, the Grayl might be better renamed ‘The Holy Grayl’ (only it’s available to all at a pretty reasonably price and without enlisting the services of Indian Jones…a few clicks will do the trick!).

Grayl Ultralight Purifier: The stats

Material:100% BPA -free: polypropylene #5, food-grade silicone, food grade ABS
Flow rate:15 seconds per 16 oz (2 liters per minute)
Lifespan:300 uses (40 gallons/150 liters)
NSF Standards:Tested to 42+53

Design features of the Grayl Ultralight Purifier

Easy-to-use one-press system

Filtering bottleSimply scoop in some water, push down the inner press, drink away! The active filter technology does the rest of the magic with electroadsorption, ultra-powdered activated carbon and silver-treated zeolites


Components of bottleThe Grayl is made up of a screw-on filter, screw-on lid, BPA-free interior press and exterior refill bottle.


Filter on water bottleThe filter removes 99.9999% of viruses, 99.9999% of bacteria and 99.999% of protozoan cysts. It also filters particulates, chemicals and heavy metals, and when you’ve used it for 300 cycles, or until the flow rate is noticeably slower, you can simply replace the filter for the next 300!

Grayl Ultralight Purifier review

Confession: when I first opened the package to the Grayl Ultralight Purifier it wasn’t love at first sight. I’m a bit of an old-schooler by nature and for the last 15 years or so have been carrying various forms of purification tablet. In the box, the Grayl looked slightly too complicated and elaborate for my fairly old-fangled tastes. It didn’t take long, however, for the Grayl to win me over.

The first thing to effect the change was a quick perusal of the specs, during which I saw that the Grayl ticked just about every box I could possibly need it to tick. It weighs only 10.9 ounces – lighter than my usual water bottle – and is of a similar size and capacity. It’s also completely BPA-free, a claim that I couldn’t make for any of my old water-bearers. Next came the most important part…

Many similar models to the Grayl claim to be ‘purifiers’ but are in fact only filters. The distinction is an important one. Filters – and, indeed, my trusty ‘purification’ tablets – are capable of removing bacteria and protozoa, whereas a bona fide ‘purifier’ will eliminate not only these but also waterborne viruses, and do so far more effectively. The Grayl Ultralight uses a purifier cartridge which captures inorganic contaminants, toxins and submicron pathogens by means of electroadhesion, ion exchange and ultra-powdered carbon. I had no idea what any of that meant, but it sounded great.

Bottle in the snow

The next bit I understood perfectly well and was good news all round. In doing all of that ion exchange electroadhesion and so on, the Grayl protects you against 99.9999% of viruses and bacteria and 99.999% of protozoan cysts. Many of these viruses, bacteria and protozoa will be ones you’ve likely never heard of but with which I, sadly, am quite well acquainted.

In the past, I’ve endured a number of hospital visits and tummy upsets on account of a fairly lax purification regime. Giardia has wreaked its horrible havoc on my bowels on three separate occasions. I’ve also had one dose of standard dysentery and another of amoebic dysentery (a whole other ball game!). During the latter of these, I happened to be on a month-long solo-trek in the Himalaya and ended up fighting for my life in a Ladakhi hospital.

As a result of these misfortunes, in the past few years I’ve been particularly careful, lugging 2-liter bottles into the mountains with me and using a fairly foul-tasting cocktail-combo of purification tablets and/or a UV pen to ensure I avoid a repeat performance should those heavy, bulky 2-liter bottles run dry. It’s not the most convenient of systems, but it has worked and above all given me peace of mind when out on my adventures.

That brings me to the next way in which the Grayl has won me over. On my first day of using the Grayl in the hills I set off with an empty bottle. My pack weight was, as you’ll imagine, considerably friendlier. While I still had some reservations about being able to adapt to such a modern-looking system, my back, shoulders and leg muscles were soon very much endeared! After an hour or so, I stopped by a stream to put it to the test, and so began something of a paradigm shift and budding love affair.

Filling water bottle

The ‘complicated’ design was about as complicated as that of your average toaster. I scooped in some water, pressed down the interior bottle and Bob, as they say, was my uncle.

The next part of my anatomy to give thanks to the Grayl were my taste buds. The water was blissfully non-chemical tasting. I’d almost forgotten what fresh mountain water tasted like and was delighted to be reacquainted. The whole process took me a grand total of about 20 seconds. I didn’t have to wait for the pills to dissolve and take effect and I didn’t have to stir the water like some demented caster of spells for ‘two-to-five minutes’ with a UV purifying stick. From now on, things would be much simpler, much tastier, and much more convenient. I was well chuffed. I felt, I imagined, more or less like Columbus had upon discovering the Americas.

Simplicity and convenience are the Grayl’s true forte. You simply pop some water into the exterior bottle, place the interior press inside and plunge it down to the bottom, letting the filter do its thing.

Later in the day I got a little bit bolder. Our hike took us over a glacier and on the way down I stopped at the foot of the ice to refill the bottle with some of the meltwater. As soon as the idea was hatched, a very vigilant part of my brain started waving its warning flags. Giardia! it was screaming. I recalled the protracted loo-time I’d bought myself the last time I’d drunk glacial meltwater, but decided to trust in my new piece of kit nonetheless (ah, the thing we do to make sure our reviews are thorough, dear reader!).

I waited patiently that evening and over the following two days for the symptoms to arrive, and had stocked up on a small squadron’s supply of loo roll and antidiarrheals just in case, but they didn’t come. A few months down the line, my supply of loo roll remains strong and my antidiarrheals untouched. I’ve been on a few dozen outings in the hills, mountains and even a few bike rides in lower-lying valleys where chemical contaminants were more likely than not. The Grayl has joined me on each adventure and become an ever-present fixture in my ‘must bring’ accessories. If you’re looking for a superbly practical, very light, super-safe and generally lovable water purifier, I’d suggest you make it one of yours, too…

(Ah, and if anyone would care for a two-year supply of mildly nauseating purification pills and a rather slovenly UV stick, they’re free to a good, patient and potentially tastebud-deprived home…)

Filter bottle

What I love the most about the Grayl Ultralight Purifier

Finding a safe, reliable and simple means of purifying water while out in the mountains has always been a bit tricky. There have always been compromises and trade-offs. With the Grayl, that isn’t the case at all. It’s quick, easy to use and the water you treat tastes, well…like water!

Other systems I’ve used have left the treated water tasting nothing short of foul and/or have required a great deal of patience or waiting time before the water is ready to drink. They’ve also been a bit fiddly or composed of multiple parts that I tend to lose alternately over the course of a year, or even a single outing. The beauty of the Grayl for me is that I simply chuck the empty bottle in my backpack and I’m good to go. It weighs very little and takes up about the same room as a 16 oz Nalgene bottle (the capacity is 16oz, the size a fraction larger due to the filter at the bottom).

Last but not least, there’s the peace of mind. Drinking from a potentially dodgy water source always brings with it a degree of finger-crossing and touching-of-wood. With the Grayl I don’t feel in the slightest bit exposed to all the potential party-poopers and microbial nasties that might sneak their way into my bottle and, ultimately, my digestive system. My fingers haven’t been crossed in quite some time, nor have they felt the need to do any touching of wood. The bottom line is that the Grayl UP is reliable, brilliantly so. I’ve already filled it from sources I wouldn’t have imagined filling my bottle from when using other systems. In month 3 AG (After Grayl), my tummy remains happily undisturbed by any of the potential blights that might befall a less well-equipped H20-drinker – something that was not always the case and not always a certainty in the dark ages BG (Before Grayl).

What I don’t love so much about the Grayl Ultralight Purifier

After a few months of using it, the Grayl and I are very much an item. Where I go, she goes. I am, I dare say, fairly smitten. If I had one little nit-picking complaint, it would be that she’s a bit on the pricey side. Then again, she is worth every penny for the peace of mind alone, not to mention all of the additional benefits mentioned above.


The Grayl Ultralight Purifier is a super-efficient, lightweight and reliable water purification system that simplifies and speeds up the whole water purification process when out in the wild. It might be just a touch pricey, granted. However, compared to the ongoing expense entailed in using other options, and given all their other drawbacks, that little bit of extra outlay is minimal and a small price to pay for all the hugely desirable benefits the Grayl offers.

Find the latest price at:
Grayl | Amazon | REI | Backcountry

Disclaimer: Cool of the Wild received this product free in return for an honest review. We only recommend gear that we love from companies we trust and we are under no obligation to give a positive review. All thoughts and opinions are that of the reviewer and we are in no way influenced by the brand or company.

About Kieran


Kieran is a nuttily-passionate climber, mountaineer, trekker, trail-runner, and all-round lover of wild places. He has spent most of his life doing cool things in the Himalaya, Rockies, Dolomites and the Italian Alps, where he now lives and spends his time stomping trails, clambering up crags, ticking-off peaks and, occasionally, sleeping (with reluctance!).

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