Robert P.wrote a review of MSR Guardian Purifier System on November 13, 2016
Familiarity: I've used it once or twice and have initial impressions
I purchased the MSR Guardian after speaking with MSR on 3 different occasions as well as several local shops. All assured me the Guardian was the perfect filter to take to the Grand Canyon to filter silty water. After filtering 15 liters of moderately silty water the filter died, all the water was being returned via the outlet hose. Following the directions, I cleaned the pressure relief valve but found it to be perfectly clean. The next step in the instructions is to replace the filter, unfortunately not an option deep in a remote section of the Grand Canyon. The filter appeared to be perfectly clean.
When I called MSR, they admitted the Guardian has problems with silty water and was told “we’ve had problems with this pump”. Of course this is unacceptable since they advertise this pump as being made for “worse case sediment”. This ruined a 7 day backpack and forced us to hike out and drive 50 miles to purchase some treatment tables. I should have had a backup but everyone I talked to about this pump assured me of it's reliability. I expected much more of this product and from MSR Customer service.