The Sawyer Gravity System (1 Gallon) is a group-sized backcountry water filter kit good for basecamp and group use. Costing $40, it comes with a 1 gallon water reservoir, hose, Sawyer mini water filter, caps and adapters, and a syringe for cleaning the filter if it starts to clog up. The entire unit weighs 8.3 oz, but drops down to 6.5 oz if you just carry the filter, hose, and reservoir, which is the minimum set of components required for field or basecamp use.
Gravity Filters 101
If you haven’t used a gravity water filter before, they usually consist of “dirty” water reservoir for holding untreated water, a hose, and water filter. Some systems, also include a “clean” reservoir so you can capture filtered water for later use without having to stand around and decant it into bottles or hydration packs.
The advantage of a gravity setup is that there’s no pumping, squeezing, or wait time (chemical purification) required to get filtered or treated water. You simply fill the “dirty” reservoir and let gravity pull the water through the hose and filter for you. This is ideal if you have to filter a large quantity of water for several people at once, or so you can set up a basecamp refill station where people can filter water when they need to refresh their supply.
The Sawyer 1 Gallon Gravity Filter includes a 1 gallon water bag, a water filter, and all of the fittings needed to operate, clean, and maintain a complete system. Most of these components can also be mixed and matched with third party components if you wish to customize your system or reuse components in other ways. Let’s take a closer look.
1 Gallon Reservoir
Sawyer includes a 1 gallon water reservoir with the unit which has a wide opening at one end to make it easier to fill and a small one for plugging in a filtration hose. The bag is made with a thick non-pliable plastic that makes it awkward to roll up in a backpack. It’s not gusseted on the bottom, so it won’t stand up on a picnic bench and has to lay flat or be hung up when filtering.
While having a wide opening for filling is very useful, you have to understand its limitations. You can’t plunge the bag into still water, like a lake or pond and expect the reservoir to fill up. It’s not like a rigid water pitcher or Nalgene bottle, since the walls are a softer plastic. The only way to fill the 1 Gallon bag is to pour water into it from above using a different container or holding the wide mouth open under a campground pump or cascade of water in a stream. The bag’s sidewalls will only expand if the water coming in is under mild pressure. This is true of all wide-mouth, soft bottle containers.
I’ve never liked the fact that Sawyer sells non-transparent reservoirs and the 1 Gallon reservoir included in this product suffers from the same defect. Transparent reservoirs make it easy to see how much water you have in the reservoir and whether it’s cloudy or full of sediment, because it can muck up your filter. Those are all things you want to know before you filter water, but they’re hard to observe if you can’t see the contents.
Most people hang gravity water filers from tree branches, so it’s strange that Sawyer hasn’t included a lanyard for that purpose. While you can easily rig up a piece of extra cord for that purpose, that’s not necessarily something that a car camper would have handy. There is a handle cutout that you can slip over a branch, as I illustrate in the top photo above, but you can’t always count on the forest to cooperate with you like that. If necessary, you can use the unit by laying the water bag on a flat surface, although it has to be sufficiently high that the water filter can hang below it for a gravity effect. Sawyer includes a small plastic support with the unit to prevent the output hose from kinking in this configuration.
Dual-threaded Sawyer Mini Water Filter
The water filter included with the unit is a new type of Sawyer Mini water filter with threads at both ends, like the Sawyer Squeeze water filter. (The original Sawyer Mini only has threads at the input end) The output side of this dual-threaded Mini has a screw-on push-in/pull-out valve at the output end, so you can turn off the flow when you’re finished filtering water and want to suspend the gravity filtration process.
The dual-threaded Mini is a 0.1 micron absolute hollow fiber member water filter that physically removes 99.99999% of all bacteria, such as salmonella, cholera and E.coli and 99.9999% of all protozoa, such as Giardia and Cryptosporidium. While it’s not the fastest filter, it can still filter a gallon of water in under 7 minutes. If the filter slows with use because impurities accumulate in it, you can backflush the filter by inserting the tip of a plastic syringe (included) filled with water into the output side of the filter to clean it out and improve the flow rate. With proper care and occasional cleaning, the Mini is rated to have a lifetime of 100,000 gallons.
The 1 Gallon Gravity System includes several Sawyer water filter accessories including a cleaning coupling, plastic tubing, a plastic syringe for back-flushing the filter, and inline hydration adapters, which are also sold separately. While they have utility with this specific water filter system, they can also be repurposed to create an inline water filter system where you filter on the go, in a gravity filter setup using a third party reservoir/bottle, screwed onto a compatible 3rd party reservoir like a Platypus or Evernew bladder, or even a regular soda water bottle.
While the Sawyer 1 Gallon Gravity System is a complete gravity water filter system, I don’t consider it a top of the line or best of breed gravity filter. The Platypus Gravity Works Water Filter System, the Katadyn Gravity BeFree 3L and the Sawyer 2 Bag Gravity Water Filter System are better featured, more convenient, and easier to use for group or basecamp use: but they’re also 2-3 times more expensive. However, if price is a big concern, the Sawyer 1 Gallon Gravity System is a decent value and a good starter system. It’s also an “open” system, where you can easily swap in components from other manufacturers over the lifetime of the product, or repurpose the components in new ways. If you backpack and camp a lot, that’s a desirable quality in any water filter system.
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