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Reviews > Hydration Systems > Bladders > Polarpak MOFLOW Hydration System > Test Report by Nancy Griffith

November 25, 2008



NAME: Nancy Griffith
EMAIL: bkpkrgirlATyahooDOTcom
AGE: 42
LOCATION: Northern California
HEIGHT: 5' 6" (1.68 m)
WEIGHT: 132 lb (60.00 kg)

My outdoor experience began in high school with involvement in a local canoeing/camping group called Canoe Trails. The culmination was a 10-day canoe voyage through the Quebec wilds. I've been backpacking since my college days in Pennsylvania. I have completed all of the Appalachian Trail in Georgia, Tennessee and North Carolina. Now I usually hike in the Sierra Nevada of California. Most of my trips are section hikes or loops from a few days to a week. I carry a light to mid-weight load, use a tent, stove and hiking poles.



Manufacturer: Polarpak
Year of Manufacture: 2008
Manufacturer's Website:
MSRP: US$31.95
US$14.95 for Shower Attachment
Listed Weight: None listed
Measured Weight:
Reservoir and Tube: 170 g (6.0 oz)
Pump: 34 g (1.2 oz)
Shower Attachment: 86 g (3.0 oz)

Other details:
Volume: 70 oz (2.1 L)
Dimensions: 6.75 in (17.1 cm) x 15.2 in (38.6 cm)
Shower hose length: 40-42 in (102 - 107 cm) attached directly to reservoir
80-84 in (203 - 213 cm) when attached to MOFLOW hose system

Photos courtesy of Polarpak

Shower Attachment


The material is listed as 100% antimicrobial film and hardware by Microban.

The hydration system consists of a 70 oz (2.1 L) reservoir with two internal baffles running lengthwise. There are two through-slots at either side of the top of the reservoir. There are no measurement graduations on the exterior of the reservoir. There is a screw cap opening near the top. Below the screw cap is a plastic fill handle. The cap is attached to the reservoir fill handle with a plastic strap. The lower portion of the reservoir has an exit port coupler where the male end of the tube is connected. The other (female) end of the tube also has a quick disconnect where the bite valve or pump bulb is attached. The bite valve is angled 90 degrees and rotates 360 degrees. The quick disconnects work by aligning the flanges, pushing down and turning clockwise to lock into place.

My initial questions after looking at the product were:
1) Would the baffles make it difficult to add ice to the reservoir since you can only fit ice cubes into the middle baffled portion?
2) Could I actually leave the pump at home or would I need it to keep the water flowing?
3) Do I miss having graduation marks?
4) Does it stand up in my pack without having a clip at the top or will I have to devise my own clip using the two slots?


Use Instructions: (wording as included from Manufacturer)
How to Use the MOFLOW System:
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 70 oz 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.

Quick Release Coupler with Shut Off Valve:
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.

Coupler Rules of Engagement:
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.

Cleaning Instructions:
1) Rinse your MOFLOW system with cold saltwater at initial use.
2) Rinsing your MOFLOW system with cold saltwater and hung to dry is suggested after every use. Do not dry clean or bleach the reservoir.
3) The entire MOFLOW system is made with Microban which is an antimicrobial ingredient built into the film, bite valve, cap, hose and couplers. Microban drastically reduces the need to clean and kills harmful bacteria.


Per the instructions, I rinsed the reservoir with cold water to which I added a few spoonfuls of salt. I sloshed the mixture around, drained it out and rinsed it a couple of times to remove all of the salt. Then, I filled the reservoir with water to nearly full and closed the screw cap. I attached one end of the hose to the lower portion of the reservoir. Then I removed the bite valve. The quick disconnect was easy to use. I then attached the pump bulb. It seemed to turn securely into place. I pumped 60 times. Then I removed the pump bulb and re-attached the bite valve. Then when I bit on the valve, the water squirted into my mouth. The water didn't come out so quickly or in such a large volume that it was uncomfortable to drink, i.e. choking me. The water did not seem to have any distortion to the taste at all.

I tried to operate the bite valve by hand too and had some difficulty. The package shows a woman squirting water from several inches (cm) away into her mouth by operating the bite valve with one hand. I was not able to duplicate this. First of all, with 60 pumps, the water did not squirt out with that much force. So, I pumped it an additional 20 times. It did squirt out with more force, but I was never able to duplicate the photo on the package.
Photo courtesy of Polarpak

Then I tried the shower attachment by disconnecting the bite valve and attaching the shower. It makes for a longer shower hose than connecting it directly to the reservoir. The shower turns on/off by pulling out/pushing in the shower head. Again, the shower did not seem to flow with much force. I raised it up providing a pressure head and it worked great. However, the intention is for the internal pressure to force the water out. The instructions say to pump 60-80 times and not to over inflate, so I did not try pumping it more.

The instructions say to stow the pump in your pack or leave it at home, so I tried to drain an entire filled bladder using 80 pumps of pressure. With approximately 1/3 of the water still in the reservoir, the water did not squirt out anymore. However, the remaining water could be accessed by sucking on the bite valve (as with other reservoirs).

I did not insert the reservoir into any pack, so it is possible that it will operate differently during actual use.


I have two backpacking trips planned for the Field Testing period in which I will evaluate the following items. I also plan to use the PolarPak for day hiking, mountain biking and running. I want to use it while running to evaluate how much the water sloshes around with the baffles. I have used other hydration packs while running and the sloshing is quite annoying.

1) Performance
a. Does the hydration system work for the various uses as advertised, i.e. shower, pillow, etc.?
b. Does the pressurized system work well for drinking or does the water flow too quickly (making me
inhale water)?
c. Does the system work well for cleaning my toothbrush?
d. Does it really make me drink more? Do I tend to overhydrate?
e. Do the bite valve and cap seal well?
f. Do the baffles keep the water from sloshing around?

2) Durability
a. How well does it hold up after sliding it in and out of my backpack and hydration pack?
b. Does the hose pump or bite valve wear out?

3) Cleaning/Taste
a. Does the anti-microbial system seem to keep the whole thing cleaner?
b. Is it easy to clean the reservoir with the baffles? the tube? the bite valve?
c. Does it distort the taste of water?

4) Ease of Use
a. Is the hose pump easy to use?
b. Is the cap easy to open/close?
c. Is the valve easy to operate?
d. Does it fit well with my backpack and other hydration packs?
e. Is there a hook or other method to hold it upright in my backpack or hydration pack?

5) Weight/Bulk
a. Is it lightweight?
b. Is the hose pump bulky? Does it tend to get misplaced?


The Polarpak MOFLOW hydration system appears to be well-constructed and as advertised on the Polarpak website except for the operation of the bite valve by hand. However, I will continue to experiment with this to see if my technique is the problem.

Thanks to Polarpak and for allowing me to test this hydration system.

This concludes my Initial Report. The Field Report will be amended to this report in approximately two months from the date of this report. Please check back then for further information.



I used the hydration system 8 days for backpacking, 5 times for hiking and once for mountain biking. For backpacking, I inserted it into my Granite Gear Vapor Trail pack between the back pad and the pack itself. For hiking and mountain biking, I used it in my Camelbak Trailblazer Hydration Pack. I used the shower attachment a couple of times while camping. Some examples of specific trips follow.

White Mountain, White Mountains (California): 10 miles (16 km); 12,470 to 14,246 ft (3,800 to 4,340 m) elevation; 45 to 70 F (7 to 21 C); packed dirt to rocky conditions.

New Dungeness Lighthouse, Sequim, Washington: 11 miles (18 km); sea level; 55 to 70 F (13 to 21 C); sandy conditions.

Mount Whitney, Southern Sierra Nevada (California): 22 miles (35 km); 8,366 to 14,497 ft (2,550 to 4,419 m) elevation; packed dirt to rocky conditions.

Mount Rainer Northern Loop (Washington): 50 miles (81 km); 1,700 to 6,740 ft (518 to 2054 m) elevation; packed dirt to rocky conditions.


On my first use, I filled the reservoir to take it in the car heading for a camping/backpacking week in the Southern Sierra Nevada. I pressurized the reservoir and got it to squirt out quite well. I really like this feature. There is something refreshing about the water coming out with pressure. However, when we stopped for dinner, the reservoir leaked and soaked my newspaper on the floor of the car. I played with the connection but it still leaked with a steady dripping. I was able to use it without pressure for a day hike. But when I pressurized it again and set it on the car seat for 30 minutes while getting ready for the White Mountain hike, it leaked all over the seat. I depressurized it, and it worked ok.

I then used it for the Mount Whitney backpacking trip without pressuring it. It worked fine for 1 day and then started leaking on our summit day. I turned it around to hold the hose close to the reservoir and it worked ok. I tried to pressurize it again the next day and it leaked all over my legs.

Customer Service Experience:

I called the phone number on the packaging for Polarpak to see what to do about my leaking system. I got the answering system which did not have a choice for Customer Service. The choices were 4 different individuals. The last choice was also a 'general' number, so I left a message there on Monday morning. I left a message again on Tuesday at mid-day. On Wednesday morning, Paul called me back and apologized for the delayed response since they were at the trade show. He was very helpful and said that they'd send out a new unit right away with a return slip for the old one. I received an e-mail with the UPS tracking a few hours later and the new system arrived on Friday. I filled the new reservoir, pressurized it and moved the connection to see if it would leak. It worked fine.

The replacement MOFLOW system worked for a mountain biking trip and a few day hikes and then for the Mount Rainier backpacking trip until the 5th day. We stopped at a stream for a break so I pulled out the reservoir to see if I had enough water to make it to camp. It was sufficient, so I put it back and pressurized it since it was nearly gone and needed pressure to continue to flow out. Immediately there was a steady leak of water from the lower coupling. I pulled it from the pack and released the pressure. It still continued to leak. I even removed the hose but it still leaked from the lower coupling. This made the reservoir completely useless for holding water. I had to pour the remaining water into my Nalgene bottle and use it as my water container for the remainder of the trip.

Upon return home, I contacted Paul at Polarpak and let him know what happened. He sent out another MOFLOW system which I received about a week later. This second replacement does not leak and is working fine to date. I'll get more use with it in the LTR phase.

Filling the reservoir at home was quite easy by holding onto the fill handle and holding it under my in-door refrigerator water dispenser. I tried to put ice cubes in the reservoir but could only fit in a small number due to the two baffles. The center section between the two baffles is the only portion where ice cubes can go.

On the trail, I filled it by pumping into a Nalgene bottle first and pouring it into the reservoir. I was disappointed that the opening did not fit my water filter/pump end snugly. My water filter/pump end fits both large and small mouth Nalgene bottle perfectly. The reservoir opening is very close to the larger size, but it is not a fit. I found the cap to be easy to loosen/tighten.

In my IR I stated that I didn't notice any distortion to taste, but when I leave water in the reservoir overnight, it definitely has a plastic taste. So, I started to rinse with saltwater after every use which did seem to help. Since I'm now using the second replacement, I'm back to having a plastic taste, but I will monitor whether that changes throughout the LTR period.

The bite valve is really comfortable to use and although it does not have a separate lock, the valve is secure. Water never leaked from it. The bite valve works easily without holding it with my hand. I typically put it to my mouth, hold it with my teeth, drink and spit it out when I'm done.

The material seems to be durable. I did not see any signs of wear during this test period. However, I am now using my third system which doesn't give a fair assessment of durability.

While the pressure system at first seemed to me to be a gimmick, I found that I love drinking water under pressure. It flows easily and probably does cause me to drink more although I am already diligent about keeping hydrated. It was the most beneficial during heavy aerobic exercise like mountain biking because I could drink quickly between my gasps for air. I have not found the 60-80 initial pumps to be sufficient to empty the reservoir (as noted in my IR). So, I had to carry the pump bulb with me if I wanted to re-pressurize the system. I didn't find pumping to seem like a hassle at all since I liked the result. But I did fear losing the bulb since I kept it in an outside pack pocket for convenient access.

It is also possible to suck water without the pressure. I find the pressure to be useful when rinsing my toothbrush.

Shower Attachment:
Of course, the shower needs pressure to flow, but it was easier to just hang the reservoir high enough to provide a pressure head rather than to pump it. Besides, a 70 oz shower is a pretty small shower. However, the biggest problem is that since I would not ever want to put unfiltered water into my reservoir, I had to pump water through my filter first. Then I'm wasting that filtered water for showering. I did it for the test, but I wouldn't bother in real life.

My 2.5 gallon water carrier is more convenient for washing up. I would fill it with water and leave it in the sun. Then, the shower attachment fit perfectly into the opening, so I just hung it up and had a nice warm shower. The on/off mechanism for the shower attachment is really handy since it is at the spray end of the shower attachment.

Use As A Pillow:
I did try using the empty reservoir pumped up with air as a pillow. I don't normally carry anything special for a pillow and just stack up my extra clothing to make one. The reservoir worked much better than that. I wrapped it with a fleece jacket to make a soft surface and found it to be quite comfortable. Depending on the amount of pumps, I could adjust the hardness/softness of the pillow to get it just right. The only down-side is that it squeaked slightly while adjusting my position during the night.

Lack of Clip and Graduation Marks:
Although there is no clip at the top of the reservoir to attach it to my packs, it turned out to not even need one. The material of the bladder is fairly stiff probably because it is made of something to withstand the pressure and since it has baffles. Plus, with the addition of some air pressure inside, the reservoir maintains its shape well enough to keep standing upright in my packs.

The lack of graduation marks really did not make a difference to me since I use a Nalgene for measuring water for cooking. I did check the volume though and found that I could only fit in 64 oz (1.9 L) of water at the beginning of the test.

I did not have any problem with keeping the reservoir clean. I typically would just drain and hang the reservoir after use. One nice thing about the baffles is that they tend to keep the reservoir open for drying. This is a good thing since a standard hydration pack hangar wouldn't work due the baffles being in the way.

The reservoir cannot be cleaned by scrubbing due to the baffles, so I put some baking soda and water inside to make a scrubbing paste and worked it around. Overall, I was pleased with the cleanliness. However, I have to remember that with the replacement units, I haven't had a fair chance to let one system show effects.


Things I like:
Pressurized water is pleasurable to drink
Bite valve is comfortable and easy to use
Baffles keep it open for easy drying
Use as a pillow
Shower attachment used with my 2.5 gallon reservoir

Things I dislike:
Leaking! This is a fatal flaw. A hydration reservoir is useless if it can't hold water.
I can only fit 64 oz (1.9L) of water into the reservoir
The cap opening does not fit my water filter/pump end
The shower attachment is not useful with the Polarpak due to the size of the reservoir and the need to filter the water first.


For the Long-Term test period, I plan to see if the third MOFLOW system can make it without a leak. I also plan to use it for running to evaluate how much the baffles reduce sloshing.

Thanks to Polarpak and for allowing me to test the MOFLOW hydration system and shower attachment.

This concludes my Field Report. The Long-Term Report will be amended to this report in approximately two months from the date of this report. Please check back then for further information.



I used the MOFLOW system 8 times during the Long-Term Reporting period for hiking and mountain biking. I also use it for a convenient water source when working in the yard, playing tennis or just driving, but those uses are not included in my total.

Foothills of the Sierra Nevada (California): 3 miles (5 km); 743 to 1,262 ft (226 to 385 m). I do this hike often so conditions varied from 60 to 70 F (15 to 21 C) in dry conditions to 45 to 55 F (7 to 13 C) in pouring rain.

Tahoe Rim Trail, Sierra Nevada (California): 2 miles (3 km); 7,377 to 7,512 ft (2249 to 2290 m); 50 to 60 F (10 to 15 C); dry conditions.

Lake Margaret, Sierra Nevada (California): 5 miles (8 km); 7,400 to 7,700 ft (2256 to 2347 m); 55 to 65 F (13 to 18 C); sunny conditions; trail was partly covered with snow.


First of all, I didn't have any problems with leaking during this test period. All of the seals remained intact. There was no deterioration in the performance in any way.

During the FR, I used the MOFLOW mainly for backpacking. But during this test period, I used the MOFLOW for day trips thus using it with my small hydration packs. I got to see how convenient it is to have the hose be able to detach at the reservoir. My hydration pack requires a bit of maneuvering to route the hose through the strap and hook it. So, if my MOFLOW is already in the pack and I need to fill it, I can just unzip the pack, detach the hose from the reservoir, fill the reservoir, insert the reservoir into the pack and re-attach the hose. No re-routing of the hose is needed.

I also used the MOFLOW with a small snow pack which has an insulated hydration tube sleeve. The detachable mouthpiece on the MOFLOW really was useful when trying to route the tube into the sleeve. It made it quite easy to traverse the entire length without much effort.

On one hike, I ran for a short distance alternating with the MOFLOW and with my other reservoir. The baffles definitely helped to prevent sloshing. I could still hear and feel the water moving around a little, but it was much reduced over the movement and noise with my other water reservoir.

The plastic taste remained evident when I would leave water in the MOFLOW overnight. But with fresh water for a day trip, I didn't find any particularly unpleasant taste. I typically open the cap, drain the water and let the MOFLOW air dry after use although I do sometimes forget to do so for a few days. I wasn't very diligent about rinsing with salt water after each use. I had no issues with anything growing in the reservoir, tube or mouthpiece.


I really like the concept of having pressurized water during strenuous activity and see the MOFLOW as a great concept. It seems that there is a flaw in the lower reservoir coupling that allows it to leak on some units, but I did not have any additional problems with leaking during this test period.

Things I like:
Pressurized water is pleasurable to drink
Bite valve is comfortable and easy to use
Baffles keep it open for easy drying and reduce sloshing noise
Use as a pillow
Shower attachment used with my 2.5 gallon reservoir

Things I dislike:
64 oz (1.9L) capacity is small
The cap opening does not fit my water filter/pump end
The shower attachment is not useful with the MOFLOW due to the size of the reservoir and the need to filter the water first.


I plan to continue to use the MOFLOW system as long as possible but will probably limit it to day trips. I wouldn't want to have a leak on a long trip. If I experience any leaking, I plan to permanently seal the coupling at the reservoir.

This concludes my Long-Term Report and the test series for the MOFLOW hydration system.

I would like to thank Polarpak and for choosing me to participate in this test.

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

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