Back in June when I was in the Lakes and in September on Dartmoor, I used the MSR Guardian water purifier. You can find all the technical details on the MSR website. Hitherto, I’ve been using the Sawyer mini filter, which is very light and easy to use. The main draw back is the slow filter rate and its susceptibility to clogging. Admittedly, backwashing with the provided syringe is quick and easy to cure clogging.
A couple of people I know have started using the MSR Guardian water purifier. On the Challenge I was given an impressive demonstration of the ease of use and impressive flow rate. The other attraction is that it’s a much more stringent purifier than the Sawyer, filtering out pretty much everything except chemicals. The downside is it is quite heavy (c.500g dry and 600g wet) and bulky.
However, I reckon it’s a good choice if you’re concerned about water quality. I’ve always been wary about small pools of static water and areas where there might have been contamination by animals or humans.
For instance, when I was on Dartmoor in September, camping at Taw Marsh, there were a lot of cattle and sheep roaming free. Even with freely running water, it’s not possible to know whether it is contaminated with faeces or not. Personally, I’d rather not take a chance. With the Guardian the chances of getting anything nasty are basically zero because it will filter out even viruses.
Some tarns in the Lake District are contaminated with human waste. At least with the Guardian you can be sure that you won’t catch anything. You can even filter water from puddles and be confident. To a degree, this can offset the extra weight of the Guardian as you can utilise any small source of water, obviating the need to carry extra water. This might be particularly useful for high camps, where you can use small pools/puddles which would be difficult with many other systems.
Two other features make the Guardian an attractive purifier. It is self cleaning, so there’s no mucking about with backwashing. It is also freeze proof, unlike the Sawyer filter, so you don’t have to worry about it in colder months.
I found it really straightforward to use. The long hose means it’s simple to put in any water source. Pumping was easy and the flow rate was impressive. The bottom of the pump mates with Nalgene bottles and “cantenes”. I use a 1L HDPE bottle and an 3L collapsible cantene/bladder. While there’s next no no leakage after use, I stow the Guardian in an Exped dry bag as the hose and pre filter remain wet.
All in all, I think this is a great bit of kit if you want absolute certainly that the water you’re using is potable (as long as you avoid chemical contamination). Obviously there is a weight penalty, although if there’s more than one of you, it soon becomes very weight efficient. For a group of people, it’s a no-brainer with the security and rapid flow rate. I will still use my Sawyer filter where water quality is better and weight is a consideration. For the rest of the time, the Guardian is my choice, especially if water sources are dubious. It is very expensive relative to other filters, but should last a lifetime.
Disclaimer: I bought this with my own money and have no affiliation with MSR