View Full Version : Gravity Filter?

11-16-2010, 13:26
Thinking about buying a gravity filter for a thru-hike in March. Has anyone used one before? We were looking at the MSR Autoflow. On a LT trail hike last year we used a MSR miniworks filter which was always getting clogged and generally being a pain in the butt. We were looking for something to replace it with.

11-16-2010, 13:44
I like my MSR Autoflow a lot. It's almost always very fast, but I like it mostly because it allows me to collect a bunch of water at once and then do other things while the water filters. When it does get slow, it's easily restored to full quickness by picking up the clean water bag and allowing it to reverse flow for a couple liters. You can save some weight by removing the cap cover and the black rubber filter cover. My only gripe is that a better stuff sack could make it much faster to deploy.

11-16-2010, 13:53
For more than one person there nice. I don't have one but saw many out there in use the popular ones are the msr and platy

11-16-2010, 14:15
I have a Platypus Clean Stream and I love it. Filters 4L in 2.5 mins. Cleaning is easy as stated above- all you have to do is backflush with a bag of clean water. As an added bonus, you can use the bag to transport more water if you anticipate hitting a particularly dry section of trail. I used to have a Katadyn Hiker and it broke on me. Having gone with both a pump and a grav filter, I would definitely recommend a gravity filter.

Odd Man Out
11-16-2010, 14:34
I have the old ULA gravity system which isn't made anymore. You could fabricate one pretty easily. It is a silnylon bag with a drawstring around the top. There is a hole in the bottom with a tube fitting for a drain. On the inside of the bag, the drain is connected to a Katadyn Pro filter. On the outside there is a few feet of tube for the clean water to flow through. Works nice and very light weight. The outflow tube can go into a regular drinking bottle or attached to a collapsible bag (platy, e.g.). in this set up, it could be left to filter unattended. When the bag fills, water flow stops until you come hook up another. This same kind of system is still available as the Katadyn Base Camp filter, although this has a much bigger and heavier bag than the discontinued ULA system.

The biggest drawback with this format, however is that the outflow from the water bag is clean water, so when filling the bag, you have to take care not to contaminate the outflow tube, which is a bit tricky if you are filling from a stream or lake.

I think the better arrangement is to have the filter at the bottom end of the outflow tube instead of inside the bag. This is used by the MSR Autoflow, Playpus Cleanstream, and Sawyer systems. If there is a quick connect attachment between the bag and the long tube to the filter, you can remove this when filling the bag. Then there is no need to worry about contaminating the outflow as this is on the dirty side of the filter. Then attach the long tube with the filter on the bottom end to the quick connect. The other advantages of this set up is the water bag could be used without the filter as a shower or sink. Also, the hydrostatic pressure needed to force the water through the filter is more reliable. However, you can't use a Katadyn filter for this as it doesn't have a tube attachment on the inflow side. The MSR and Platy systems seem to use the same filter. Sawyer uses their own (which seems to be lighter). Sawyer sells the parts to build your own system, which is what I would like to do using my lightweight sylnylon bag from the discontinued ULA system.

11-16-2010, 16:37
I used the Platypus this year. It was great for 2 or 3 people, but maybe overkill for just 1. I go through a lot of water, so it worked well for me. In the cold you have to be sure not to let it freeze, storing it in a dry bag will let you bring it safely into your sleeping bag on the cold nights. I always backflushed about a quarter liter every time and the filter was still working fine when I got off the trail at about half way.

11-17-2010, 09:43
I began using the Platypus gravity filter last year and so far have been very satisfied. The two 4-liter bladders supply more than enough water for camp which is where I tend to consume lots of liquids. My only question is how effective it may be when water has to be obtained from a shallow pool. Has anyone had to deal with this?