Gravity filters are continuing to get a lot of hype, and for good reason. They’re easier to use.
Gravity filters and classic pump filters work via the same cleansing elements, except the gravity system does all the work. No pumping is required. That’s a big advantage. Having an easier process means campers will to drink more water — and that’s always a good thing.
I first started using gravity filters while guiding youth groups. I found the students were too lazy at times to squat down by the water’s edge and pump water; and without drinking enough water they became cranky, slothful and even sick. By hanging a gravity filter in a tree at camp, the students would gather around it like a watering hole. It made a huge difference.
A gravity filter eventually replaced my pump filter on family trips. The switch was for the same reason. It was easier. Even my daughter — who was six at the time — would fetch water without complaining. The only real issue was gathering water while en route. Using a pump filter alongside your canoe or kayak still makes more sense then trying to hang up your gravity filter alongside your boat like a blood transfusion bag.
I’ve used the Platypus gravity filter for a few years now, changing over to the two-litre to four-litre when travelling with larger groups. It’s lightweight, compactable and fast, considering it works solely on gravity. The filter also lasts for quite a while, providing over 1,500 litres of water. But you have to make sure you’re aware how to purge it — or what my daughter calls “burping” the filter.
For this season I started trying out the MSR Autoflow Gravity Filter. It was a bit cheaper and had many similarities to the Platypus system. It’s lightweight, durable and works with a similar hollow fiber filter design to eliminate protozoa and bacteria (take note that gravity filters do not deal with viruses). I even picked up the new MSR stainless steel Alpine-bottle, which I’m happy with now that I got used to the Adapter Lid that works together with the filter.
The filter time for the MSR Autoflow was about the same as the Platypus. However, it didn’t come with the two-bag system. That means you have to place the output hose into your water container to fill up, rather then fill up a bag of water and then dispense it into separate containers. Of course, you can easily buy a separate bag for the MSR if you wanted, which is what I ended up doing.
I prefer the idea of hanging up the gravity filter and walking away while the storage bag is being filled up. It’s somewhat silly to just wait for each separate container to fill. With that said, however, my students I took on a spring hiking trip didn’t have a problem with this at all. They found the Platypus storage bag had a tendency to spill over and they had to start the process all over again.
The extra storage water bag for the MSR Autoflow also means you can purge — or burb — the filter when it starts to get clogged and slow down. Without it, you’d have to backwash. You disconnect the hose from the main storage bag, turn a clean bottle of water upside down, and flush it backwards to clean out the filter. Sounds simple but I find burping is quicker... and my daughter still gets the giggles every time I do it.
Whatever gravity filter you choose, I think it will definitely change your trip. It has for me.