MSR Trail Base Water Filter Kit Review

© Toby Archer

The MSR Trail Base Water Filter Kit is an interesting beast. When I was first asked to review it I was rather sceptical. My scepticism hasn't completely gone, most notably around the kit's price, but it has to be said that I've found it considerably more useful than I imagined at first.

Refilling water bottles on a hot day in the Welsh mountains  © Toby Archer
Refilling water bottles on a hot day in the Welsh mountains
© Toby Archer

So what is it? The Trail Base kit is a versatile water filtering system built around MSR's slightly older TrailShot microfilter. It can be used as a mini hand-pump filter, a larger gravity-fed filtering system, or just as a water carrier. The filter itself is effective against almost all bacteria and the vast majority of protozoa, as well as particulate matter. For pretty much any use in the UK or abroad, this is all the filtering power you'll ever need.

The TrailShot was reviewed last year for UKC/UKH by Richard Prideaux. Partly as a result of that review I bought myself a TrailShot and had been using it when backpacking or bikepacking on my own, for half a year or so, when I was asked to review the Trail Base. The heart of the Trail Base Kit is a slightly adapted TrailShot micro filter. This can be used on its own exactly like the stand-alone TrailShots. Indeed, I passed my little-used TrailShot on and now use the filter unit from the Trail Base Kit in exactly the same way when weight is a priority.

Back in the glorious summer of 2018 (we will tell our grandchildren how dry the mountain crags were!) the filter unit went into my pack for most days out.

On one of those perfect days I climbed (well, let's be honest, I seconded) The Grooves on Cyrn Las. We finished off all our water after doing that but day was still young and the conditions just perfect so we refilled our bottles from Llyn Bach below Clogwyn y Ddysgl using the filter part of the Trail Base Kit before enjoying the early evening sun on the Gambit Climb.

Trail Base Kit filter unit being used alone, in hand-pump mode
© Toby Archer

Filter unit attached to the 'clean' bag, and filtering water by gravity
© Toby Archer

Using the unit this way, you filter the water through via a hand-squeezed pump system. It is very simple, easy to use and quite effective although I have used other filters with a more efficient and faster pump system, for example the much more expensive MSR Guardian purifier - see my review of that on the left. If you use the filter unit of the Trail Base kit alone, then everything said by Rich about the TrailShot remains true.

The TrailShot, or the filter unit from the Trail Base Kit when used alone, works well for someone on their own. MSR claims it filters at about 1 litre a minute. My personal experience is that they might be slightly optimistic about that. You are squeezing with your hand, and while for a litre this is no great issue, by the time you've filled two litres or more it starts getting a bit dull.

Flowing water, but still plenty of people and livestock around - would you trust it?  © Toby Archer
Flowing water, but still plenty of people and livestock around - would you trust it?
© Toby Archer

For this reason I wouldn't want to use a Trail Shot if part of a small group or, indeed, as a solo backpacker who was trying to filter three or four litres in one go. This is where the other bits of the Trail Base Kit come into play – the two water bags and the hoses that join them via the filter unit. One, with a roll-top for easy filling from a stream or similar, is very clearly marked "dirty water". The second, without a roll top, but a screw-on cap that includes a little flick out spout, is marked "clean water". The tube from the dirty water bag screws onto the 'in' tube of the filter unit. The spout of the filter unit then clicks into a valve on the clean water bag. Hang the dirty water bag up somewhere high, and gravity moves the water down through the filter so that clean water fills the lower, clean water bag.

With the proviso that you find somewhere to hang the upper bag, this works very well, and with no pumping on your part you'll soon have two litres of filtered water at the ready. This works excellently at a camp and, as long as you have enough receptacles, you can filter with ease enough water to fill tomorrow's water bottles, to cook with, water to make drinks with, water for a bit of basic face washing and teeth cleaning, and so on.

Filtering that amount of water using just the squeeze pump on the TrailShot, or even with a lever pump such as on the Guardian, would be a complete pain, so the gravity-fed function of the Trail Base is a definite advantage. However, it may go without saying that finding somewhere to hang the upper bag can be a bit of an issue in the UK uplands. I found that using the Trail Base in Finland was very easy as you are never far from a tree. In Scotland, making use of Scotland's forward-looking outdoor access code, I've used an open car door to hang the upper bag from, but when camped away from the car we had to improvise with a precarious tripod fashioned out of logs that less responsible campers had presumably dragged there to burn.

Hanging it up is no problem when you've got plenty of trees
© Toby Archer

But in the deforested UK hills you may have to improvise
© Toby Archer

So, if the pump-filter alone works just like the rather good TrailShot, but also combines with the bags to make an efficient gravity-powered filter system, what's not to like? For me the big question is value for money. The RRP for the Trail Base Kit in the UK is £120 whilst the TrailShot is £45. Because the filter unit of the Trail Base Kit is, basically, a TrailShot, it does rather feel like you are paying £75 for two water bags and a bit of hosing.

Yes, in some ways, that's an unfair criticism – you are buying a versatile system with the Trail Base. The practically minded could probably bodge a TrailShot into a gravity-fed filter, although you can imagine any dribbles from where a dirty water hose met the in-hose of the filter would lead to dirty water running down over the filter and into your supposedly clean water bottle or bag, completely negating the whole thing. You don't get that with the Trail Base – MSR are a proper engineering company and all the various bits of the kit click or screw together with reassuring firmness. But still, 75 quid is a lot of money.


The Trail Base Kit actually IS more than a sum of its parts, being both a handy, light pocket filter that you squeeze to pump AND a gravity fed filtering system that works well for pairs, families or even small groups who need to filter plenty of water. Hence, for some people the cost may well be justifiable. On the other hand, for many a TrailShot on its own will probably be enough. Yes, squeeze-filtering four or five litres of water in one go would be a total pain, but if you've never needed to do that or do it very rarely, saving a lot of money is likely to outweigh the occasional tired hands! But if you regularly want to filter multiple litres of water when out in the wilds, but also want a small lightweight pump filter that can be used on its own, then the Trail Base Kit may well be worth the money. As a system it does work very well.

MSR say:

To meet the needs of multi-activity backcountry adventurers, we set out to engineer the most versatile water filter ever. The Trail Base microfilter kit features modular components that allow it to be used as a gravity system at camp, a pocket-sized filter on the trail, or a fast-and-light reservoir when you need to carry clean water with you. Whether you're hiking, biking or basecamping, the Trail Base water filter kit offers incredible flexibility and options, making it the one filter that truly adapts to your adventure and the filtration task at hand.

  • Effective Against: Bacteria (99.9999%), protozoa (99.9%) and particulate. Hollow fiber filter meets U.S. EPA drinking water standards* and NSF protocol P231 testing standard
  • Versatile: Modular components allow system to quickly and easily transform from a 2 L gravity system into a small trail filter and back
  • Simple Transitions: Trail filter simply quick-connects into gravity system to create the complete gravity-fed filter system
  • Complete Kit: Includes ultralight, durable clean water reservoir, which features our 3-in-1 cap for easy filling, drinking and pouring

For more info see

Support UKC

As climbers we strive to make the kind of website we would love to visit, with the most up-to-date news, diverse and interesting articles, comprehensive gear reviews, breathtaking photographs and a vast and useful logbook system. As a result, an incredible community has formed around the site - we’ve provided the framework but it’s you who make the website what it is today. If you appreciate the content we offer then you can help us by becoming an official UKC Supporter. This can be a one-off single annual payment or a more substantial payment paid monthly or yearly which includes full access to Rockfax Digital and discounts on Rockfax print publications.

If you appreciate then please help us by becoming a UKC Supporter.

UKC Supporter

  • Support the website we all know and love
  • Access to a year's subscription to Rockfax Digital.
  • Plus 30% off Rockfax guidebooks
  • Plus Show your support UKC Supporter badge on your profile and forum posts
UKC/UKH/Rockfax logo

No comments yet

Loading Notifications...
Facebook Twitter Copy Email LinkedIn Pinterest