If you have not used a gravity system for filtering water, we suggest you try one. Filling a bag, hanging it and being able to forget it while you make camp or have lunch is how we like to filter water. Call us lazy, but when we are enjoying the sunset as it drops below the horizon and we know we will have clean water the next morning without pumping or using chemicals we feel pretty good going to sleep.

Over the years we have used many different water purification products. From iodine tablets, chlorine, 4 different types of MSR water pump purifiers, Steri Pen, Life straw and a gravity filtration system by Platypus. Recently MSR came out with the TrailShot a small hand pump water filter, then integrated it into the gravity system that is called Trail Base Water Filter Kit. It uses a hollow fiber filter system to remove bacteria. This means that you can use as a gravity filter and a hand pump as well. When hand squeezing, the pump pushes water right into a bottle and one does not have to wait for the water to run through the gravity system. It’s nice for short hikes when packing the bags needed for gravity filtration is over kill. It’s a very multipurpose solution to purifying water.

It comes with 2 2-liter bags: one dirty and one clean, two hoses and a pump filter. We replaced these bags with larger bags from Platypus. When used as a gravity system, you fill the bag that is labeled dirty, set up the system and hang the dirty bag higher than the clean bag.  Then go cook dinner as your filter cleans 1 liter of water per min (if the filter is clean).The filter connects directly into the clean bag or if you have a compatible system, can be connected directly into your hydration bladder.

We discovered through trial and error that the filter requires back flushing every day.  We were filtering fairly dirty water with lots of sediment and on average filtered 7 liters per day. This step didn’t add much time to our routine, but if we skipped it, the filter would get clogged. If you are filtering water with lots of sediment, we recommend pre filtering that water going into your dirty bag with a bandana or coffee filter as this will help prevent clogging.

The only complaint we have is that the cap on the filter comes off easily. This happened often to us while filtering, resulted in a complete loss of our water, requiring us to refill the bags and start over. It is fairly easy to mitigate by being careful when placing the filter, but it was extremely annoying.

Pros
Just hang it up and leave
Light weight
Multi-functional- can be used as a hand pump filter

Cons
The cap comes off easily
Requires back flushing more often than other gravity systems
Water bags included in the kit were too small for our purposes
Not as fast as most hand pump systems

Modifications

We did some modifications to the bag system. We did not like the roll top of the included bags and needed more water capacity.  We used 3L Platypus hydration bags instead. The bags have a slide locking system that ensures the closure of the ziplock style top. We marked one bag Dirty and one Clean with a permanent marker (which wore off eventually). We really like the durability of these bags- they lasted the whole trip with no leaks and lots of abuse.

We made a small hose attachment with a valve on the end to allow us to fill our hydration packs and have the convenience with the in line valve to use as a spigot.

Conclusion

With modifications this is a great multi-functional water filter that you can use for short hikes or as a gravity system. We give this a 4 out of 5 stars as the cap falling off really needs to be fixed.

We would definitely recommend this to others.