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Reviews > Hydration Systems > Bladders > Polarpak MOFLOW Hydration System > Test Report by Edwin L. Morse

December 14, 2008



NAME: Edwin Morse
EMAIL: ed dot morse at charter dot net
AGE: 71
LOCATION: Grawn, Michigan USA
HEIGHT: 5' 8" (1.73 m)
WEIGHT: 145 lb (65.80 kg)

I started backpacking in 1979 with two weeks in northern Michigan along the Lake Superior shore. My gear was cheap, heavy and sometimes painful. My starting pack weight was 70 lbs (32 kg) with food but no water. Since that first time I have made one and two week trips in Michigan, Maine, New Hampshire and Pennsylvania. Late last summer I did a 2 week hike on Isle Royale. My starting pack weight was 32 lbs (14.5 kg), including 10 days of food and 3 qt (2.8 l) of water. I am slowly learning what lighter gear works for me.



Manufacturer: Polarpak
Year of Manufacture: 2008
Manufacturer's Website:
Moflow Pressurized Hydration System MSRP : US$31.95
Shower attachment MSRP : US$14.95
Listed Weight: N/A
Measured Weight:
Reservoir: 3.5 oz (99 g)
Hose: 1.9 oz (54 g)
Bite valve: 0.2 oz (5.7 g)
Pressure bulb: 1.1 oz (31 g)
Shower attachment: 2.9 oz (82 g)


The Moflow hydration bladder, hose, bite valve and pressure bulb all came in a stiff clear plastic "bubble" package stapled to a pasteboard backing. The pasteboard backing and the clear plastic had a standard type slot cut in the top so it could be hung on a display shelf. This package is 8.75 in (22 cm) wide and 21 in (53 cm) long.
Moflow System in package
Still in the package

The shower attachment came in a separate soft clear plastic envelope that was sealed shut.
I've been using hydration bladders for several years. My first thought when I took all the parts out of the package was "Wow, this is totally different than anything I've seen."

The bladder itself is a soft grayish opaque and strong feeling plastic (doesn't the word plastic cover a wide range of materials?) material, the fill cap and reservoir exit port coupler are a hard yellow plastic. The word "Microban" is stamped in the side of the bladder. In much smaller letters under this is stamped "antimicrobial product protection". There are two slots at the top of the bladder, one on each side. I can imagine tying the bladder to a tree with these slots to use the shower attachment.

The hose is also marked antimicrobial. I measure the hose to be 41.5 in (105 cm) long, including the hard plastic connections at each end. The yellow right angle bite valve swivels easily.

The pressure bulb is gray and about 3.25 in (8 cm) long and 1.75 in (4 cm) wide and fits easily in the palm of my hand. The connection tube and swivel adds another 2 in (5 cm)


The following instructions were on a small sheet folded inside the package.


1. Disconnect hose from reservoir exit port coupler.
Remove reservoir from pack [if needed) and fill with
water. Make sure cap is screwed on tight after filling.

2. Reconnect hose to reservoir exit port coupler and
put reservoir in pack.

3 While wearing pack disconnect bite valve from
hose coupler and attach pump system. To fully
pressurize 700z reservoir squeeze pump bulb 60-
80 times. [Do not over inflate)

4. Disconnect pump system and reconnect
bite valve. Stow pump in pack or leave at
home. Pump can be disassembled for
easier storage.


1. Rinse your MOFLOW system with cold saltwater at initial use.

2. Rinsing your MOFLOW system with cold salt water and hung to dry is suggested after every use. Do not dryclean or bleach the reservoir.

3. The entire MOFLOW system is made with Microban which is an antomicrobial ingredient built into the film, bite valve, cap, hose and couplers. Microban Drastically reduces the need to clean and kills harmful bacteria.


The MOFLOW system comes standard with two quick release coupler
systems. One is located at the exit port on the reservoir and the other at
the bite valve end of the hose.

The exit port coupler is designed so you can disconnect the hose allowing
you to remove the reservoir and leave the hose system assembled in the
pack. This is ideal for cleaning and filling purposes. Each coupler includes a
shut off valve preventing liquids from exiting when disengaged.

The bite valve coupler is designed so you can disconnect the bite valve and
attach the pump system for pressurization.


To assemble couplers. grasp the swivel and line up the flanges with the
two channel guides in the coupler. Press down or in and turn to the right
90 degrees. You will be able to feel the stopping point. Do not force or over
twist couplers."


I carefully followed the instructions at the kitchen sink. I washed the reservoir with salt water, then ran clear tap water through it several times to get all the salt out. Instead of filling from the faucet I used a measuring cup to see for myself how much water the bladder would hold. I could only pour in 7 cups (or 56 oz (1.66 L)). On the package it states "70 oz." (2 L). This is 14 oz (41 ml) less than claimed. Will the bladder stretch as it is I use it?

I put the System in a hydration pack and went for a walk. The instructions say the pump can be left at home but I decided I should take the pump and the instructions. After I initially squeezed the pump 80 times I soon had trouble getting water from the bite valve. I stopped twice during a 4 mile (6 km) walk to pump in more pressure. I think I will carry the pump along on all my testing. I also keep the pump in a small ziplock bag. This gives me a safe place to put the bite valve while using the pump. I have not yet been able to squirt water from the bite valve as shown on the website. I drank the reservoir dry while walking 4 miles (6 km).
After drinking the reservoir dry
Empty reservoir and pump



The Polarpak Moflow Hydration System is an interesting concept. I found I tend to drink water faster during the brief experience I've had with the system. I need more hiking experience with this hydration system before I have much confidence in using this interesting concept.

Positive thoughts:
The contents under pressure is an interesting idea
The water comes out quickly when I bite just right on the bite valve
I like the use of antimicrobial materials.

Negative thoughts:
The reservoir does not hold as much as claimed on the package
I have not yet been able to squirt water as shown on the website
Frequent pumping is needed to keep the contents under pressure.

I'm not sure yet if the frequent pumping is required because the system looses pressure (I might not have had the cap tight enough) or if it is because as water is removed there is less total volume so more air is needed to maintain pressure.

This concludes my initial report.



During the last two months I've done eight day hikes on trails, eight trail work days in the Manistee National Forest (MNF) and on property of Consumers Energy Company (CEC) just north of the MNF, as well as two backpacking trips in the same areas. In addition I've done ten long days of bushwhacking while searching for property corners for the local Land Conservancy on four preserves within 30 miles (48 km) of Traverse City, Michigan.

The weather has varied from bright and sunny with high temperatures of 84 F (29 C) while backpacking down to steady rain and temperatures of 50 F (10 C) on one trail work day.

The terrain in the MNF is generally rolling sandy hills covered with oak and pine forests, with a few swamps and creeks for variety. The terrain on Land Conservancy property is steep oak and pine covered hills or low swamps with cedars, hemlock and thick under brush, which is a challenge for bushwhacking and trying to maintain a compass bearing.


Overall I would say the Moflow hydration system did fairly well. I've been using hydration systems for several years. I have both positive and negative thoughts about hydration systems in general.
I especially like the large fill opening of the Moflow for warm weather use on day hikes and trail work days because I can put in several ice cubes when I fill the bladder. It is easy to fill the bladder with water from the kitchen faucet. When the system is under pressure I like the way my water comes out quickly when I bite on the mouth piece and there is no need to suck to get a drink. I have had no leaks in the system, when I remove the hose from the bottom of the bladder I will get a few drops of water which I see as no problem.

On the negative side I have just a few minor complaints. I have to carry the pressure bulb with me so it is easily accessible when I hike. I had started carrying a fanny pack with my backpack and this seems to be the ideal place for me to carry the pressure bulb. It is an added task to pressurize the system after filling the bladder. When I drink about half the water in bladder I have to use the bulb to build more pressure again. I have not yet found an easy way to fill the bladder when backpacking. So far the best way I've found is to filter water into another container and then pour it into the Moflow bladder.
Filling the Moflow bladder
Filling the Moflow bladder
On my two night hike when I started packing the first morning I didn't get the hose properly connected to the bladder (known as operator error). When I tried to get a drink after walking for a while I could get no water. I had to stop and take nearly everything out of the pack to properly attach the hose.

One of my negatives seems to apply to other hydration systems I've used but not (at least not yet) to the Moflow. I have had unpleasant experiences with another hydration system in my tent while backpacking and had to mop up water after I rolled over on a bladder a few times. One time I had put a full bladder in my empty pack with the hose attached so I could get a drink during the night. Somehow the bite valve got under my air mattress. I discovered the problem when I woke about 2 AM then I had to move nearly everything in the tent to clean up the water. Fortunately my down quilt was all on top of the mattress. When I'm ready to sleep for the night I now put all water outside under the vestibule. I did use the Moflow bladder as a pillow for reading one night but when I was ready to sleep I put the bladder outside with the rest of my water. Next time out I will try it for sleeping since I'm getting confidence that the system won't leak when under outside pressure. It appears that the Moflow automatic shutoff valves have solved this problem.


I've used the Polarpak Moflow hydration system for a total of about 30 days of hiking in the last 2 months. In my opinion it is not possible to pump enough pressure into the system when the bladder is full of water to maintain pressure until it is empty. When the bladder is down to about half I have to use the pressure bulb again for 70 to 80 pumps. I think the cause is decreasing volume rather than a pressure leak as I first thought it might be. I still have not been able to squirt water out by squeezing with my fingers as shown on the website. I've tried this several times to show others how the contents are under pressure. Sometime soon I will try a pair of padded pliers since it could be that my fingers are not strong enough.
I've measured the volume several times. I now believe the bladder holds 2.0 liters (2.1 quarts), as advertised.
I like the Moflow system for day hikes, especially on the hot days when I should drink more. I don't like it very much for backpacking or trail work because of two "fiddle factors". The first "fiddle factor" is the difficulty in filling the bladder. So far the only method I've found to fill the bladder when I'm backpacking is to filter into another container and pour into the Moflow bladder. I have two more ideas I will try, either day hiking or backpacking. The second "fiddle factor" is the problem of keeping pressure in the system to easily get a drink. When I'm trying to get work done I don't like to stop to add more pressure to the system.


In addition to continued use of the system there are a few specific things I will be trying. I will use the shower attachment. If I can't get a warm day in this area I will take it along on our annual trip to Florida in November where it is always warm.
I will try to find a more direct way to fill the bladder while backpacking. I have two ideas that might work. I will also try the bladder for a sleeping pillow since this is one of the suggested uses.

This concludes my Field Report.



The weather has varied from cool to cold for most of my hikes during the last two months. The high temperature while I was hiking was 70 F (21 C) one sunny afternoon, while the low temperature was 22 F(-6 C) when I was eating breakfast at 6:00 one morning. There have been a few rainy days and a few bright sunny days. Several mornings have been frosty as well as cold. Mostly the terrain has been rolling hard wood and pine forests.

I've been on at least ten day hikes, including two after sundown. I've also done one two night backpacking hike and three over night hikes. All except one of the backpacking hikes were in the Manistee National Forest in northwest Lower Michigan.

The third overnight was in the Ocala National Forest (ONF) in Florida. The weather was cooler than I expected in Florida but not much different than late summer in Michigan. The high temperature for this hike the first two days of December was 64 F (18 C) with a low in the morning of 38 F (3 C). Michigan is relatively flat compared with New England or the western states but Florida is really flat. In the ONF there were still oaks and pines but the prevalent plants I recognized were the palmetto, live oaks and long leaf pines.

Day hikes were in the MNF, the Sleeping Bear Dunes and the Pere Marquette State Forest. I've used the Polarpak Moflow hydration system for all hikes I've done in the last four months.


I think the Moflow hydration system is very good for drinking on day hikes - after the system is pressurized. I still find that pumping up the pressure is a small irritation but the faster and easier drinking makes it worth the effort.

I've started carrying a small belt pack on all hikes as well as the backpack. This lets me keep a few small items in easy reach, including the bulb to add pressure to the Moflow bladder. I've found that the bladder pressure seems to be much reduced when the bladder is down to about half full. I have, a few times on an easy trail, pumped up the pressure while still walking slowly. The second time the pressure begins to go down I know the bladder is nearly empty. This is a warning I don't have with other hydration systems that I've used.

Another 'problem' is filling the bladder. Filling is easy at home with the kitchen faucet. Filling the bladder in camp is not so easy. With other systems, both hydration and bottles, I can fill directly from my MSR filter outlet hose. With the Moflow bladder I have to fill another container first and then pour the water into the Moflow bladder.

I've planned several times to take a shower when backpacking but it has just been too cold during the testing period. In early October I tried it in my backyard even though it was only 50 F (10 C).
backyard shower
washing my hair in the backyard

I got my hair washed but soon ran out of water in the bladder. Perhaps in warm weather and with more practice I could at least wash off the worst stink on a longer hike.

I was very apprehensive about using the bladder for a pillow on overnight hikes. I tried it first in the backyard where I could retreat to the house if I got everything wet. I had the bladder about three fourths full. I was worried that when I put pressure on the bladder it would let water flow out and soak everything. There was no problem with leakage. The automatic shutoff valves work just fine. I could use the bladder empty and inflate with air but I like to have all my water filtered at night and ready for morning. I would like to have the bladder in the pack as well but that would not work well for a pillow.

After three overnight hikes I've found that I like to use a shirt or jacket folded on top of the bladder for my pillow, both for more thickness and a softer place for my head. When I was on the third overnight hike, in the ONF in early December, I used a hammock for the first time while backpacking. The Moflow bladder worked very well for a pillow with two shirts folded around it.

I was able to fill the bladder directly from the hand pump, which is much easier than filtering water and then pouring it into the bladder. I had brought an extra Ziploc bag so I could pump into the Ziploc and pour into the Moflow. The small stream that the pump produced let me pump directly into the Moflow bladder.

my campsite at Hopkins Prairie
Hopkins Prairie campsite

Here is my campsite at Hopkins Prairie in the Ocala National Forest, after filling all my water containers at the pump. Even with all the advantages (pump, tables, firepits and outhouses), I decided again that I prefer not to camp in established campgrounds.

I had assumed that in Florida it would be warm enough to use the shower attachment. Wrong again - when I got to camp the temperature was 55 F (13 C) and falling. I washed my hair but it was too cold for me to do anything more. The bladder was nearly empty again just washing my hair.

While I'm hiking I throw the hose and bite valve over my shoulder to keep it out of the way. This lets me take off the pack and set it on the ground without getting the bite valve in the dirt. With a quick twist of my shoulder the hose falls into my hand. When I got back to the Juniper Springs Campground I asked the young lady ranger to take my picture.
end of a hike
bite valve over my shoulder

In this picture you can see the bright yellow bite valve hanging over my right shoulder.


I've enjoyed testing the Polarpak Hydration System. I've been using hydration systems for years but never had used a bladder for a pillow. With this system I now have confidence to use the bladder either empty or full of water. I prefer to fill all my water containers at night, so I also use the bladder full of water for a pillow.

When under pressure the water comes out fast when I bite on the mouth piece,
I can use the bladder for a pillow and not worry about water leaks,
The shower system works,
The bladder is easy to fill from a faucet or hand pump.

It is an added hassle to pump pressure into the bladder when it is refilled,
The bladder does not hold enough water for a full shower,
The opening does NOT fit my water filter so it is more hassle to fill the bladder when backpacking. If the screw top opening would fit the outlet adapter on my water filter I think I could filter directly into the bladder while it was lying on the ground. This is not totally speculation since I've poured water into the bladder while it was lying flat beside the kitchen sink. If my filter outlet hose fit the bladder opening I could tie the bladder to a tree and fill it directly from the filter.

There are two changes I would like to see in this system. First change the size of the fill opening so it will fit popular water filters. Second, make a larger size bladder available so it is possible to take a complete shower.

I will continue to use the system in spite if the little problems, since the advantages still outweigh the disadvantages.

This concludes my Long term Report on the Polarpak Moflow hydration system.

I would like to thank Backpackgeartesters and Polarpak for the opportunity to test this interesting hydration system.

This report was created with the Report Writer Version 1. Copyright 2008. All rights reserved.

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