Reviews > Water Treatment > Filters > Sawyer One-Gallon Gravity System > Test Report by Richard Lyon

Sawyer offers its one-gallon gravity filtration System in two configurations. I shall be testing the Sawyer 1-Gallon Gravity System (SP160), which has five principal components: starting from the left in the photo, one gallon [3.78 liter] plastic water bladder, gravity hose [pictured with fittings on both ends], mini filter, cleaning plunger, and cleaning coupling. With this System I'll supply the vessels for filtered water. The Sawyer 1-Gallon Dual Bladder Gravity System (SP2160) comes with two bladders, one for "dirty" [unfiltered] water and the second for the "clean" [filtered] end product, and several additional components to facilitate water flow.


Manufacturer: Sawyer
Website: sawyer.com [Note: Sawyer products are not offered for sale on the website. Sawyer will direct a user to online and brick-and-mortar stores where the products may be purchased.]
Filter material: 0.1 Micron Absolute Hollow Fiber Membrane
Capacity, listed: "up to 100,000 gallons" [378,000 liters] [Using either measurement, plenty or water!]
Filter Weight, listed: 1.22 lb [550 g]
Height, listed: 12.6 in [32 cm]
Dimensions, listed: 7.25 x 2.75 in [18 x 7 cm]
Component weights, measured: bladder 3.75 oz [106 g]; gravity hose with fittings 1.25 oz [35 g]; mini filter 1.38 oz [39 g]; cleaning plunger 0.75 oz [106 g]; cleaning coupler [0.1 oz [3 g]; bladder cap 0.25 oz [7 g]; arm 0.12 oz [3 g]; spare O-ring 0.25 oz [7 g] total 7.85 oz [296 g]
Dimensions, measured: hose 26.5 in [67 cm] long; bladder 12 x 14 in [30 x 36 cm], filter with cap 5.2 in [13 cm] long
MSRP: Not available

I cannot explain the discrepancies between listed and measured items above, of which the filter weight is the most puzzling.

How It Works.

A MINI, an in-line filter that Sawyer also sells as a standalone product, does the work of removing bacteria [99.99999%] and protozoa [99.9999%] from untreated water. Assembly and use are easy - fill the bladder with water, attach the gravity hose to the outlet to the bladder and the MINI, and let gravity do the work. No pumping necessary. The bladder may be hung using its handle or laid on a flat surface. Note that the plastic fittings on the ends of the hose may be removed.

Included accessories can facilitate filtration. By screwing the push-pull white cap on the MINI outlet, as shown in all photos in this Initial Report, I can easily turn the water flow on or off - useful if changing bottles for the filtered water or just for storage A simple screw-on cap for the outlet on the bladder [third from right in photo above] allows carrying water from source to camp without dripping or losing water, or for in-camp storage. The System also includes a plastic arm that clips on to the bladder outlet [second from right] to reduce the risk of crimping, and a replacement O-ring for the MINI [on the right].

The handle on the water bladder makes carrying a full gallon from stream to camp very easy. The handle also makes a more reliable hook for hanging than the small loops or rope handle I have found on other gravity filters. Another simple yet functional design feature is printing on the water bladder directions for backflushing the MINI. That's easy too - screw the coupling on the clean-water end of the MINI, fill the syringe with clean water, fit to the coupling, and press to force the water back through the filter. Sawyer recommends several doses, until the water comes out of the inlet valve clean. Sawyer also recommends frequent backflushing, a practice I heartily endorse based upon problems caused by my neglect in the past.

Trying It Out

I ran two gallons through the System, using tap water, and everything worked as advertised. For the first gallon I hung the bladder from a peg on the wall, into a three-liter water bladder and then a one-liter Nalgene. For the second gallon I laid the bladder flat on a step, draining the water into the same vessels.

Initial Likes

Wide mouth on the water bladder. Should make it easier to fill in the backcountry.
The handle. Makes carrying easy.
The MINI outlet cap. Easier to operate and more reliable than an in-line clamp.
Light weight

Initial Dislikes

No instructions included with the product or on the website. And setup was not entirely intuitive; some trials and errors were needed.
No storage bag included. Easily fixed with a two-gallon Ziploc bag for everything but the bladder, which folds up easily.
The bladder outlet is on the corner, not vertical. It takes some tipping to get the last bit of water through.

FIELD REPORT - December 31, 2021

Field Conditions

Circumstances - a gimpy knee and an on-a-whim ten-day trip to Italy - limited my use of the Sawyer System to a few overnight car camping trips to fishing holes here in Montana. I won't disclose exact locations, as one or two may have been in spots in which overnight camping was prohibited, but all were at established fishing access points here in the Treasure State. Temperatures ranged from as high as 75 F [23 C] during the day to near-freezing or slightly below at night. No precipitation and no other noteworthy meteorological conditions. I drew water from big rivers - clear and clean to the naked eye, from watercourses lined with ranches full of cows, bison, sheep, or other domestic animals, not to mention the wild critters. Nothing I'd drink straight-up except in an emergency.

Performance

Like other gravity filters I've owned, operation is easy. Set it up as described in my Initial Report and let gravity do its work. I've had a few issues to deal with, all of which I've handled fairly easily and all of which I believe will diminish after more practice. I will say that the wide mouth on the dirty water bladder makes it reasonably easy to fill it from moving water. I prefer the screw-on cap to the slider system used on other gallon bladders. Takes a bit longer to fill, but is much easier to open and close and reduces the risk of drip.

First two performance issues are consequences of having to provide my own container for the filtered water. Unless that vessel is one gallon or larger, I can't walk away and let it drip unless I don't mind wasteful overflow. Often in the past I've filled gravity filters just before bedtime and awakened to a slug of potable water sufficient to accommodate breakfast and my next morning's hiking. I intend to address this matter by purchasing a second one-gallon bladder, probably from Sawyer in order to ensure that I can screw it into the Sawyer MINI. [Note that the Dual Bladder system includes the second container.] Until now I've had to mind the flow into successive one-liter containers. In this process the Outlet cap on the Mini comes in really handy. Simply screw it closed and there's no drip until the clean water container is replaced - and no splash and loss of water when an in-line clamp slips, loosens, or falls off.

The second problem is being sure that the Mini is well inside the clean water container; otherwise I risk a wind that blows the hose and filter aside. Avoiding this mini-disaster [pun intended] means finding a spot to hang the dirty water bag that allows a deep drop. Not a problem when car camping as the door handle of my car works well. When hiking I can usually find a rock of appropriate height to work, though the less-than-vertical drop, exacerbated by the corner nozzle, requires holding the bladder upright to extract the last bit of filtered water.

Even though field filtration has not included "dirty" water with algae or other debris I have backflushed the Mini after every trip, using the process I described in my Initial Report. As the flushed water came out clean after the first flush, that finished the operation.

I haven't used the filter enough to give a reliable report on durability. I can say that there's not much that can go wrong as long as I heed the simple preventive measures noted above. If the stated capacity of 100,000 gallons [>350,000 liters] be accurate, I'm unlikely to need a replacement anytime soon. And should I break something most parts - including the Mini and water bladder, which I consider the most likely to suffer injury - are available individually.

LONG TERM REPORT - May 1, 2022

Field Conditions

Field testing was limited by weather and trail conditions. My only use on an overnight trip was a hike on skis to a Forest Service cabin in early April, temperatures from 40 F [5 C] during the day to 18 F [-11C] at night, overcast skies, strong winds, and a couple of minor snow flurries.  There was a small stream nearby, and I drew water from that as an alternative to melting snow. Three fillings and filterings into a second Sawyer water bladder - early afternoon, early evening, and early morning, so I covered most of the temperature range. The stream water was clear, with minimal algae and no debris.

I've also used the filter on daylong fishing trips on Nelson's Spring Creek, Depuy's Spring Creek, and the Gallatin River. Temperatures from 35-60 F [2-16 C], cloudy weather. On the spring creeks I could hang the filter in a shed first thing and filter water while I fished, returning to the shed for lunch. Fishing on the Gallatin means spending time at one put-in point, fishing the available stretch of river, then driving to the next point and repeating. I hooked the dirty water bag to a car door at the first stop and again used a second Sawyer bag for filtered water. All stream water was clear with scant debris.

Performance

I was careful to secure the Mini well inside the filtered water bag, and with nearly vertical hangs the system handled each gallon in about twelve minutes. While I always started with clean, clear water I still consider this an excellent result, certainly more than adequate for the conditions I faced and, I expect, all of my hiking and backpacking requirements. Few of my hiking breaks are shorter than twelve minutes, and once set up and filled the system does its job unattended if the lower bag's capacity is one gallon or more.

My admiration for several components of the system has only increased. The wide mouth allows instant filling if I can stand in the water source, which was especially easy on my fishing days as I was wearing breathable waders. It's dicier but still fairly easy if I must remain on the bank whether I need to dip the bladder in the water or can use a cooking vessel to scoop up water. As noted in my Field Report, the Outlet Cap eliminates drip when passing the Mini from one Nalgene bottle to another. Assembly has become second nature with even the minimal practice I've had. The handle makes carrying easy without losing a drop.

Storage is as easy as setup and use - roll up the water bladders and pack everything else in a Ziplock bag, and stuff into my pack.

After each trip I have backflushed the Mini upon returning home. After the overnight it took two rounds until the water ran clear; only one flush was necessary on all the others.

Summary

For many years I have relied upon chlorine dioxide tablets or liquid for water purification, reserving gravity filters for larger group use on service trips. The simplicity, ease of use, and rapid performance of this system may just change this longstanding habit. Last fall I noticed a hiker with a gravity filter attached to the front of his backpack, filtering as he hiked. Not sure I'll go that far, but the Sawyer One Gallon Gravity System will see ample future use both in camp and on the trail.

What I Like

Easy to use
Reliable
Easy to maintain

What I'd Change

A small storage bag for the components would give greater protection.
A second bladder for filtered water. If I ever need to replace the system I'll go for the Dual version.

Acknowledgment

My Test Report ends here, with thanks to Sawyer and BackpackGearTest.org for the opportunity to test this simple yet highly functional product.

Reviews > Water Treatment > Filters > Sawyer One-Gallon Gravity System > Test Report by Richard Lyon