Polarpak MOFLOW Hydration System
Test Series by Kurt Papke
Initial Report - August 6, 2008
Field Report - October 1, 2008
Long-term Report - November 25, 2008
August 6, 2008
Backpacking Background: Mostly in Minnesota - have hiked all of the
Hiking Trail and Border Route.
Preferred/typical backpack trip is one week. Some hiking in
Colorado, North Dakota and Oregon. Mostly Spring/Fall
Comfort-weight hiker: I try to carry as few items as possible, but do
not go to extremes to reduce weight of items carried. Because of
my physical size & weight I consume a lot of water when I hike, at
least 1 gallon (4 liters) per day including meals, even more in hot,
|| Kurt Papke
|| 6' 4" (193 cm)
|| 220 lbs (100 kg)
|| kwpapke at gmail dot com
|City, State, Country:
|| Minneapolis, Minnesota USA
|Year of manufacture:
|Weight as received:
||Reservoir with hose & bite valve: 6.1 oz (174 g)
Pump: 1.23 oz (35 g)
Shower attachment: 3 oz (84 g)
|Capacity: 70 oz (2.07 l)
Reservoir dimensions: 6.75 in x 15.2 in (17.15 cm x 38.6 cm)
|Capacity: 59 0z (1.75 l)
Reservoir dimensions (empty): 7 in x 15.5 in (17.8 cm x 39.4 cm)
||Reservoir: $31.95 US
Shower attachment: $14.95 US
Polarpak MOFLOW hydration system was received in two packages:
1. (right in picture) The reservoir, supply tube, bite valve and
2. (left in picture) A shower head accessory system
MOFLOW is a moderately-sized (2 qt/l) water vessel that can be put
under pressure to facilitate drinking. The pressure reduces the
need to suck from the bite valve when drinking in the field.
According to the Polarpak website the pressurization encourages the
hiker to drink up to 30% more water, and thus in theory to stay more
The reservoir is filled from a water source by unscrewing the large
orange cap which is visible in the photo at left. Once filled,
the cap is screwed back on. In my initial tests I found very
little torque was required to get a water-tight seal with the screw
cap. Note in the product information above that I was only able
to fill the reservoir to about 85% of the manufacturers listed
capacity. It may be possible to attain the full 70 oz (2 l) of
water, but I was not able to do so before spilling lots of water.
Next the supply hose is connected to the exit port coupler at the
bottom of the pack with a 90-degree twist motion. I found
connecting the hose to be straightforward, and I received positive
reinforcement of a proper connection when the connector popped out very
slightly when engaged, and will not unscrew without pressing in on it.
Next the pump is connected (before the bite
valve is) as in the picture at left. Note that there is also an
option to connect the pump directly to the exit port without using the
supply tube. The bulb is squeezed 60-80 times forcing air into
the reservoir. I found with a full bladder that 80 squeezes gave
me very tight pressure. Any more pumping beyond this caused
pressure to bleed from the pump, making it difficult to over pressurize
Once pressurized, the pump is detached and replaced with the bite
valve. Note that unlike most reservoirs the MOFLOW has valves at
both coupler joints that prevent water and air from escaping.
To drink from the system, bite down on the valve with the teeth, or
(in theory) squeeze with the fingers to squirt water into the
mouth. No matter how hard I tried with my fingers, I could not
get the bite valve to squirt unless I bit down on it.
For use as a
shower, the bite valve or supply tube is disconnected and replaced with
the shower head/tube assembly as shown in the photo at left.
The resultant shower from the head is shown in the photo at right.
Operation of the
valve on the shower head took me a few moments to figure out as there
were no instructions with it, but its really quite simple: pull the
head itself and a slide valve as shown in the photo at right allows
water through the head.
Polarpak states that the entire system is made with Microban
antimicrobial material which obviates the need to clean the system
with bleach. In fact the instructions expressly forbid the use of
bleach on the system components, and recommend rinsing with a salt
Hanging/packing: the reservoir has two
hanger slots at the top corners. I have a daypack that has a
hydration sleeve and hangers for a hydration pack, and I found that the
reservoir fit the sleeve nicely and mated well with the hangers (see
photo at left).
has made this system as simple to use as possible, given that it
requires more connecting/disconnecting of valves and pumps than most
hydration systems. The shutoff valves in the exit port and supply
tube make the pressurization of the reservoir painless, and avoid
wasting precious water in the field.
One potential usability
concern is the lack of a clip for attaching the supply tube or bite
valve to a pack shoulder strap. In the photo at left a small hole
in the bite valve assembly seems
like it might be able to be used to attach to a shoulder strap with
some elastic bands, but I'll have to play with this in the field to see
how it works out.
Capacity: my "kitchen
tests" seem to indicate that maximum pressurization of 60-80 squeezes
will not allow evacuation of the entire reservoir. My experience
was about 60-70% use before it ran out of pressure. Note that
this is not a serious issue, as mouth suction can be used to drink just
as with a non-pressurized system.
Flow rate: with a full
reservoir and pressurization, I found that the system would deliver
about 50 ml (1.7 oz) of water in 10 seconds.
This concludes my Initial Report on the Polarpak MOFLOW hydration
- Accessibility: do I find it convenient to access the pump to
on a hike?
- Reliability & robustness: any leaks? Does the bite valve get
teeth marks from me biting down on it? Any wear and tear on the
- Functionality: do I really drink 30% more water with a
pressurized system? In an arid climate this may not be a good
thing, as I could burn through my water faster than I wish. How
well does the Microban prevent mildew or funky odors from
forming? Can I really wash my hair (or maybe even more of me...)
with the shower head?
- Aesthetics: how do I feel about pumping up the unit in areas
other people are present? Do people ask me if I'm taking my blood
- Packability: do I find the pump and shower units stow easily?
- Weight/benefit ratio: the MOFLOW adds some weight over a
traditional reservoir with the pump and (optional) shower head.
After several months of use
do I find that the weight and space consumed are worth the upsides?
- Polarpak also claims the reservoir can be used as a pillow.
Makes sense, as it can be pumped to any desired hardness. I am
excited to try this in my Hennessey hammock, as I've long wanted a
pillow, but didn't want to carry the extra weight. It'll be
interesting to see how well this system multi-tasks.
My principle use of the MOFLOW was on a 1-week backpacking trip to Isle
Royale National Park in Michigan September 8-14. Temperatures
during this trip ranged from a low of 40 F (4 C), to some daytime highs
around 75 F (24 C). Altitude ranged from a low of about 620 ft to
a high of 1371 ft (190 to 420 m). Terrain ranged from swampy
lowland to granite ridgelines. Daily mileage ranged from 5-13
miles (8-21 km). Water for the hydration system was purified from
lakes with a pump filter system.
I carried the MOFLOW reservoir in the
hydration sleeve of my Mountainsmith Boundary pack. As can be
seen from the photo at left, the MOFLOW is tall and narrow, and my
pack sleeve seems more designed for a shorter but wider reservoir.
Even though the reservoir extended up well beyond the sleeve, it fit in
the pack. The bite valve and tube were easily fed through the
hydration system openings in the pack.
I carried pump bulb and showerhead in the packlid where
they were easily accessible without having to open the pack.
MOFLOW did not come with a clip for attaching the tube/bite valve
to my pack strap for easy access. I improvised and borrowed the
clip from another hydration system as can be seen in the photo at
right. This worked great and kept the bite valve accessible.
Use as a Shower
One of things I like to do after several days on the trail is wash my
hair. On Day 3 of the trip I broke out the MOFLOW showerhead,
filled the reservoir with water, and tied the reservoir to the support
rope of my hammock:
Though the reservoir was fully "pumped"
with air, I found that to get decent showerhead pressure some gravity
was needed to assist, and my hammock provided a good spot to get it
elevated. The hanger slots in the reservoir worked well for
looping a hanging rope through. I found that I could shampoo my
hair with about half of
the water in a full reservoir. After I finished, I turned the
system over to my hiking buddy who can be seen using the unit to
shampoo his hair in the following photo:
This all worked quite well, and made us feel clean and refreshed.
Use for hydration
Filling the reservoir
The first difficulty I ran into with the MOFLOW was filling it with
purified water from my filter system. This presents several
- The shutoff valves on the supply tube are incompatible with my
- The fill opening is incompatible with the adapters my filter
system supplied - the opening is just a bit smaller than a standard wide-mouth Nalgene
- If the reservoir is set horizontally on the ground the water
flows out of the opening
- The reservoir is too limp to stand up vertically while filling
The solution I found through trial-and-error was to use my empty
Gatorade bottles as an intermediary. Their mouth exactly matched
the opening on the reservoir, so by filling two 1-quart (.95 l)
Gatorade bottles and dumping them into the reservoir I had a good fill.
My first use of the MOFLOW was along the Minong Ridge trail on a fairly
cool day, where I was concerned that I wouldn't drink enough water and
hoped that the pressurized hydration system would encourage me to drink
more. That strategy was successful: by noon I had emptied the
reservoir. I had to re-pump the system about
half-way through the supply of water to maintain pressure. During
the day I found the
system very easy to use: just bite down on the valve and my mouth
quickly filled with water, more than I would normally drink from a
hydration system. I attribute this to the lack of effort in
drinking: normally with most systems I have to "suck" the water
through the bite valve, but drinking from the MOFLOW was effortless.
The second use of the system was a rainy day, hiking from Little Todd
Harbor to Hatchet Lake. After an hour or so on the trail I
noticed that the bottom of my pack was quite wet, more than I would
have anticipated given that it was not raining very hard (yet). I
had my rain jacket on and my gear in waterproof stuff sacks, so I
didn't worry too much. A few hours later I observed that the
reservoir was empty, even though I had not drank all that much. I
guessed that the system had developed a leak, but I didn't know where
When I returned home I did a standard test for a leak: inflated the
reservoir and submerged it in a tub of water to check for bubbles, and
as can be seen in the photo below the system had developed a leak at
the tube/reservoir connection point:
By wiggling the tube I determined that the leak would only occur if
there was pressure down on the tube/valve assembly - if it was left to
float free it did not leak.
I contacted PolarPak customer service, and they did not have a
replacement unit in stock to send to me. They promised to send me
a replacement O-ring for the drinking tube fitting, as that is the
failure point they have seen, and received a lifetime supply (10) of
three days later. I asked them if I should superglue the fitting
to permanently seal it to continue to test if the O-ring did not solve
the problem, and they agreed that would be the best path forward.
I replaced the O-ring, and it slowed the leak, but did not stop it
completely. Looks like the rest of the test will be done with a
Use as a pillow
I like to use a pillow when I sleep on my side in my hammock. The
following picture shows the MOFLOW wrapped in a cotton T-shirt to make
it more comfortable, positioned at the head end of the interior of the
I found the fully-inflated MOFLOW made a very comfortable pillow for
side-sleeping, though I did notice my ear hurt a bit in the morning, so
I may have over-inflated the pillow and made it too hard. The
rectangular shape of the MOFLOW made it easy to orient the "pillow" in
different directions depending on how much support I was looking for
and how I was laying. I let some air out of the reservoir and
tried it again the next night, and it made a huge positive
difference. Properly inflated, this makes a great pillow.
- Positive water pressure encouraged me to stay hydrated.
- Showerhead was a pleasant way to keep my hair clean.
- Nice pillow, great multi-tasking!
- No leaks!
- Make the system easier to fill. Either the fill opening
should be the same size as a standard wide-mouth
Nalgene bottle, or supply a fitting compatible
with a filter hose.
- I cannot pressurize the reservoir enough to use the entire
contents without re-pumping.
- The size of the reservoir is not big enough for me to shower my
entire body - I run out of water when I try to rinse the soap off.
Long Term Report
Long Term Report (LTR) period my principle use of the MOFLOW was on a
4-day backpacking trip along the Southern end of the
Superior Hiking trail in Northern Minnesota from October 13-16.
This trail section varies in altitude from 650 to 1200 ft (200 to 365
m). The terrain is forested with granite outcroppings.
Temperatures ranged from a high of 60 F (16 C) to a low of 28 F (-2 C)
The MOFLOW is pictured at left with the Gatorade bottles I used to fill
it during the trip, and the filter I used to purify the water.
The rivers and streams I fetched water from were very high in tannins,
which my filter does not remove.
Prior to departing on this trip, I superglued the fitting between the
drinking tube and the reservoir to permanently stop the leak.
This was effective, but also meant that I could not disconnect the
drinking tube and had to take it with me when filling the reservoir as
can be seen in the photo.
- I used the MOFLOW extensively during this trip, and became
accustomed to the pressurized water flow. I stayed well hydrated
during the cool weather, which I credit at least in part to the ease of
drinking from the MOFLOW system.
- The water I filled the MOFLOW with during this trip had a lot of
tannins in it. The MOFLOW was resistant to staining from the
water and I could detect no off-flavors after filling the bladder with
tap water when I returned home.
- Precisely because I became accustomed to the pressurized water
delivery, it became more irritating to me when the MOFLOW ran out of
pressure while it still had plenty of water remaining. When there
is no pressure in the reservoir, the MOFLOW requires a fair amount of
effort to drink from.
- On one occasion I re-pressurized the reservoir when it was
nearly empty, though I was not aware of that condition. After
drinking a few mouthfuls of water, I got a
blast of air injected into my stomach. I discovered that the
MOFLOW can be a very effective device for inducing belching. This
experience made me a little wary of using the MOFLOW when I was not
sure that it was fully topped up with water. This is actually a
consequence of one of my general gripes with hydration bladders, I
cannot see how much water is left in the system without removing it
from my pack.
- The necessity of carrying Gatorade bottles with me to refill the
reservoir became irksome. I never seem to have enough hands when
I am pumping water, and the need to carry an extra bottle just because
I could not fill the MOFLOW directly irritated me after a while.
- I did not carry the showerhead with me on this trip. The
temperatures were pretty chilly.
- I often ended up drinking from the system after the pressure was
depleted. It is a pain to stop hiking, take off my pack, dig the
pump out of the pack, disconnect the bite valve, hook up the pump, pump
up the reservoir, disconnect the pump, stow the pump, put the bite
valve back on, and put my pack back on.
My bottom line after testing the MOFLOW for 4 months is that I am
unlikely to continue to use the system in its current design
configuration. The critical issues for me in priority order are:
I see great value in having a hydration system that encourages people
to stay hydrated. If Polarpak can address some of these issues in
future revisions of the product I think they would have a product I
- I don't trust the fittings. I don't want to carry a system
that I am worried is going to leak. Gluing the fittings solved
the problem during the Long Term Report period, but I am concerned that
the glue could fail with age or cold temperatures.
- The value of the pressurized water delivery for me is not worth
the additional weight, bulk, complexity and pumping effort.
- The problems with filling the reservoir have nothing to do with
the pressurized system, but nonetheless I find filling the system very
- The showerhead adds little value, but does add weight and bulk to
my pack. I am able to shower or wash my hair using a standard
unpressurized reservoir using gravity and its drinking tube.
This concludes my report on
the Polarpak MOFLOW Hydration System.
Many thanks to Polarpak and
BackpackGearTest.org for the
test this product.
Read more reviews of Polarpak gear
Read more gear reviews by Kurt Papke