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Reviews > Water Treatment > Filters > Platypus Cleanstream Gravity Microfilter > Test Report by Michael Williams


INITIAL REPORT - May 21, 2009
FIELD REPORT - July 21, 2009
LONG TERM REPORT - October 06, 2009


NAME: Mike Williams
EMAIL: mlebwillATyahooDOTcom
AGE: 35
LOCATION: Milliken, Colorado, United States
HEIGHT: 5' 9" (1.75 m)
WEIGHT: 249 lb (113.00 kg)

I was introduced to backpacking as a teenager through scouts in Colorado Springs, Colorado and fell in love with it. I continued to actively backpack through college and took a break to start a career and family. A few years ago we decided as a family to become very active in hiking, backpacking and camping. Currently my wife, son (7 yrs) and I hike and backpack extensively in Colorado and South Dakota as a family. We continually look for the right balance of lightweight, durable, comfortable and safe gear for our family to enhance our outdoor experiences.


Product Description

Manufacturer: Platypus
Year of Manufacture: 2009
Manufactures Website:
Listed Weight: 13.7 oz (388 g)
Measured Weight (full): 14.1 oz (400 g)
Measured Weight (w/o storage sack): 13.4 oz (380 g)
Measured Weight (w/o Clean Hose, Clean Reservoir and Shut-off clamp): 9.25 oz (262 g)
Filter Media: Hollow Fiber
Filter Pore Size: 0.2 microns
Listed Flow Rate: ~ 1.75 L / min (1.85 US Quarts / min) - depending on filter conditions and water quality
Filter Life: ~ 1500 L (1,585 US Quarts ) - depending on filter conditions and water quality
BPA Free
Reservoir Capacity: 4 L (140 oz) each reservoir
MSRP: $89.95 US
Warranty: "Limited Warranty, Cascade Designs, Inc. ("Cascade"), to the orginal owner ("Owner") under intended use and maintenance, warrants the enclosed product ("Product") to be free from defects in materials and workmanship for the life of the Product."

The Platypus Cleanstream Gravity Filter (henceforth referred to as the Cleanstream or filter) is a water treatment solution that utilizes the force of gravity to flow untreated water through a filter device to produce filtered, drinkable water. The Cleanstream is comprised of 5 major parts; the Dirty Reservoir, Dirty Hose, Clean Reservoir, Clean Hose and the Filter Cartridge. The filter works by filling the Dirty Reservoir with non-potable water, elevating the filled reservoir above the filter and the Clean Reservoir and allowing the dirty water to flow through the Filter Cartridge. Once the water has passed through the Filter Cartridge it collects in the Clean Reservoir and is safe to drink.

The Filter Cartridge is comprised of a Hollow Fiber Membrane (HFM) which is a collection of small porous tubes that create a barrier that blocks particles larger than 0.2 microns from passing through. With a Filter Cartridge that has an effective range to 0.2 microns, the Cleanstream meets all EPA (Environmental Protection Agency) standards for the removal of bacteria and protozoa which include Giardia and Cryptosporidium. The filter does not protect or treat water born viruses which would require the addition of chemical treatments in conjunction with the filter and the process is described in the owner's manual. Additionally the HFM filter should not be used to treat chemically contaminated water as chemical contaminates are often smaller than 0.2 microns.

Both reservoirs are constructed similarly out of a durable, BPA free plastic that has a zip-top closure system as well as a webbing style handle at the top of the bag like reservoir. Other than being clearly marked as the Dirty or Clean Reservoir, both bags are identical with the exception of the hose connection points. The Dirty Reservoir includes a female quick connect adapter built into the surface of the bag while the Clean Reservoir includes a screw cap connect imbedded into the lower right corner of the bag.

The purpose of the quick connect that is built into the Dirty Reservoir is to allow the user to stop the flow from the reservoir by disconnecting the hose. The Dirty Hose (shorter hose) connects to the male portion of the quick connect and to the Dirty Hose Barb of the Filter Cartridge. Alternately the longer, Clean Hose Connects to the Clean Hose Barb of the Filter Cartridge and then connects to the Clean Reservoir through the screw cap connector. The screw cap of the Clean Reservoir can be used to integrate all standard Platypus brand hose adapters to the reservoir.

Filter Components

Kit Contents:
* Dirty Reservoir (with built-in female quick disconnect fitting)
* Male quick disconnect fitting
* Clean Reservoir with reservoir cap
* Filter Cartridge
* Dirty Hose (12 in / 30 cm)
* Clean Hose (48 in / 122 cm)
* Shut-off clamp
* Cleanside barb cap
* Storage sack
* Instruction manual (9 languages)
* Filter test guide

Filter Storage

Initial Impressions

My experience with water treatment while backpacking has been limited to chemical treatment and pump filtration systems. While chemical treatments are highly effective and easy to use for providing safe drinking water, they can be time consuming and do not improve the taste of the water. Pump filtration on the other hand is relatively quick and dramatically improves the taste of the water while offering protection against most water contaminates with the exception of viruses. However, pump filtration systems can be bulky, heavy and require a good deal of effort to pump the water.

The Platypus Cleanstream Gravity Filter is an interesting solution to a backpackers water treatment needs. The product appears to offer the best of both worlds, the ease of chemical treatment with the speed and hopefully taste of pump filtration systems.

While researching this filter I developed some significant expectations as well as questions regarding this product.

1. Can the Clean side of the system multitask as a hydration bladder?
2. What is the product's ability to handle particulates in the water and will it clog easily?
3. In the event of a filter clog how effective is the suggested back flush process?
4. How great of an opportunity is there for cross contamination exposure between the clean side and the dirty side?

After receiving the product I am unsure that the Clean Reservoir can multitask as a hydration bladder (question # 1) due to the zip-top style closure of the bag. To test the closure system of the reservoir I filled it with 3 L (100 oz) of water, inverted the bag and applied gentle pressure. This test was performed 3 times and I experienced failure once; while it did hold up 67% of the time, I believe is a large risk to take.

The Dirty Reservoir does not contain any type of pre-filter or screen that could be used to remove particulate or silt that could clog the filter (question # 2 & 3). The instruction manual includes detailed instruction on how to back flush the filter in the event of a clog and indicates that this process should be performed regularly to maintain maximum flow efficiency. After receiving the product it appears easy to back flush the filter, however I am still unsure of what the impact would be in the field and how effective the filter will be with high silt water sources.

The instruction manual suggests that the filter system should remain connected at all points to minimize the possibility of cross contamination (question # 4) as well as a suggested storage procedure. I still see areas of possible cross contamination and have concerns with this aspect and will most likely not follow the suggested storage methods. The reason that I see an issue with the suggestion is that at some point the clean section will need to be disconnected to get the filtered water out. I see a potential for the dirty hoses and a dirty reservoir that has been dipped into contaminated water and has residual water on the exterior that could drip on the clean side; there is a chance for cross contamination the minute the unit is disconnected.

In addition to my expectations / questions prior to receiving the product, there are a few observations / items that are worth noting now that I have received the filter to test.

Assembly of the filter is quite easy and very intuitive; however, if needed the instruction manual provides detailed step by step instructions that are easy to follow. These step by step instructions also include warnings that appear to be critical items in the successful maintenance and long term care of the filter. The following tips / warnings in relation to the Filter Cartridge are included in the instruction manual and lead to my speculation that the Filter Cartridge is fragile and should be treated with care.

1. "Handle Filter Cartridge carefully because a damaged filter cannot prevent exposure to harmful microorganisms. Test filter for damage if dropped 5 feet (1.5 meters) or greater onto a hard surface. (See Filter Test Guide.) If filter is damaged discontinue use and replace cartridge."
2. "Never allow Filter Cartridge to freeze because freezing the filter will permanently damage the internal fibers. Always wash and dry filter parts after use."
3. "Disinfect filter thoroughly before long-term storage to prevent growth of mold, mildew and bacteria. Never use a dishwasher or microwave to disinfect parts because the high heat will damage or melt them."
4. "Clean the cartridge by backflushing it before each use to prevent silt build-up and extend the filter's lifespan."
5. "Trapped air in the Filter Cartridge will affect water flow. Purge air by filtering some water (0.1 L, 0.13 US Quarts) into the Clean Reservoir and the lifting it above the Dirty Reservoir."

The HFM filtering method is a new application to water treatments for backpacking. I am very interested to see what the results of using a filter system that does not incorporate activated charcoal to improve the taste of the water. While I'm confident that the water will be drinkable, I hope it will be enjoyable as well.

Additionally I believe that an alternate set up can be utilized in an effort to save weight. If using a water bladder such as a CamelBak, Platypus Hoser or something similar in a hydration system, it appears that these units could be used as the Clean Reservoir. Simply use the Drinking Hose of the hydration system as the Clean Hose when connecting to the filter.

Initial Report Summary

While there are still some unanswered questions, I believe that the Cleanstream will be an improvement over my current pump filtration system. I am very excited to be testing this product and have high expectations that this filter will become my primary water treatment source.

This concludes my Initial Report. The Field Report below are the results of the first two months of testing the Cleanstream.


Field Conditions

The Cleanstream has accompanied me on 4 overnight backpacking trips and a few day hikes in the mountains of Northern Colorado. The conditions the Cleanstream encountered while being tested ranged from an elevation of 5,000' (1,524 m) to 13,000' (3,962 m). Temperatures averaged 60 F (16 C) to 85 F (29 C) during the day and 35 F (2 C) to 55 F (13 C) at night. Unfortunately it was quite windy and rained on every trip the Cleanstream was used on.

I attempted to plan trips that would offer a wide variety of water sources and I believe that I was successful in using the filter in all available water sources in my area. These included slow and fast running streams, natural mountain springs, snow pack runoff, stagnant water sources and a crystal clear alpine lake. Each source of water offered a different quality of water to filter and ranged from heavy to light silt as well as leaves, branches and pine needle particulates.

One of the Water Sources

The first trip the Cleanstream was put to use was a Memorial Day weekend trip with an elevation of approximately 9,000'. During the trip the Cleanstream provided all drinking and cooking water for a group of 8 (5 adults and 3 children) in addition to a dog. The water sources used during this trip included snow pack runoff, a rain basin cistern as well as 2 natural springs. For the remaining trips the Cleanstream provided all drinking and cooking water for a group of three (2 adults and 1 child) with the dog. During these trips the water was primarily sourced from mountain streams, however one trip the water was sourced from a spring fed alipine lake at tree line.

Answers to Initial Questions

During the initial review I noted a few questions that I had from my initial impressions. Through field use these questions have been answered.

1. Can the Clean side of the system multitask as a hydration bladder?

Answer = Yes and No. While the clean bladder supplied with the system is a great receptacle for receiving and storing filtered water it can not be used as a bladder in a hydration system. However, Platypus makes a wide variety of hydration system bladders that could be used as the clean side bladder. Additionally I have found that other brands of hydration bladders use a similar diameter hose which could also be hooked up to the filter as the clean side bladder.

2. What is the product's ability to handle particulates in the water and will it clog easily?

Answer = Adequate / better than I thought it would. I was pleasantly surprised by the results I received on this. While I previously questioned if the water would need to be pre-filtered I assumed that the system did not have an integrated pre-filter mechanism; I was wrong. As noted earlier the dirty bag included a quick connect coupling as the outlet that was imbedded into the surface of the bag; during the initial observation I questioned why the bag was designed this way. This feature is critical in allowing the particulates and sediments to settle to the bottom of the bag in an area that will not flow out of the bag. It essentially creates a gravity powered pre-filter, however it may require significant time to settle before this feature is fully effective. There were situations where I did not want to wait for the water to settle before filtering, this did clog or slowed the filter with relative ease.

Sediment Settling

3. In the event of a filter clog how effective is the suggested back flush process?

Answer = Very easy and effective. The back flush process is incredibly easy and works fairly well. The issue that I had with the process is that when using a water source that is heavy in particulates and silt the back flush process is required far too often. Admittedly, allowing the silt to settle below the quick connect before starting the filter will help relieve this issue I did have situations where I did not want or have the time to wait. When I was in these situations, I found myself babysitting the filter more than I would have liked to.

4. How great of an opportunity is there for cross contamination exposure between the clean side and the dirty side?

Answer = I still feel it is there. Any time that the system is disconnected there is a possibility for cross contamination. While I don't think that the clean side or the dirty side could get confused with each other I believe that they may come in contact with each other and dirty water could contaminate the clean portion. An example would be that the zip tops never really close all that well, so it is possible for unfiltered water to enter / drip into the clean bag. Do I feel this possibility is greater than other filter products? Probably no, I could make the same contamination questions for other filter products. Will this possibility convince me to not use this filter? Absolutely not, there is always an inherent risk that I accept in the back country and I would be at the same risk by simply washing my hands in a lake and not sanitizing them afterward.


I believe that I have used the Cleanstream in a manner that has allowed me to form an opinion. So far I like the filter and believe that it has its place in my gear closet, however it is not an every trip piece of gear. The Cleanstream has some fantastic features and benefits and generally works well and there are some situations that the Cleanstream will not be my first choice.

I did run into a few situations where I found the design of the clean stream to be less than desirable. I discovered that I don't like to get my hands cold and wet when filling the dirty bladder, but each time I went to fill it up I couldn't help myself. Additionally it was very difficult to hang the bag above tree line, a lack of trees meant that I had to hold the bag or rig something with a boulder and rope. After the first use I was never able to get the zip-top closure system to work again, I understand it is great for cleaning but I found it to be unpractical in the field. Finally the Cleanstream is named accurately and should not be confused with Clearstream as the filtered water always had a yellow tint and I'm sure the water was clean, but it wasn't clear. While these critiques are minor, they are not issues that I have had with previous pump style filters.

Even with the criticism I have listed above the Cleanstream does excel in other areas. For medium to large groups I would not hesitate to bring the Cleanstream with me, simply put it processes a lot of water in a short amount of time. I would consider it overkill for solo or small groups with little water needs, but larger parties are truly where this product shines. One of the advantages of having the large 4L (140 oz) clean bladder was water storage, if you needed water it was hanging in the tree with 4 more liters (140 oz) of dirty water right behind it waiting to be filtered. Post trip cleaning was incredibly easy, a quick soak in bleach water and a little dry time on the counter was much quicker than other filters I have used.

Filling a Packed Hydration Bladder

The most surprising thing about the filter was that the gravity system would fill a bladder up while it was packed. I had the assumption that the pack would offer too much pressure resistance and the force of gravity would not be enough to fill the bladder but it did. This was great as we did not have to unpack our packs to get the hydration system out to refill on the trail and we could take smaller volume hydration systems since fill up was so easy.

Things I Like

1 - Flow rate and high output volume
2 - Ease of use with less silty water sources
3 - Ability to fill hydration systems while packed
4 - Easy to maintain and clean
5 - Relatively lightweight for large volume of treatment

Things I would Change

1 - Zip-top closure is a poor design choice
2 - Relatively heavy when used for small volumes (a smaller volume dirty bladder option would be nice)
3 - Inclusion of an in-line carbon filter to improve clarity of filtered water (maybe as an optional component)

Field Report Summary

So far I like the filter. It has its Pro's and Con's but it has its place in my gear closet and I will bring it on trips that this product is suited for. The water tasted good, but the yellow hue may turn some people (my wife) off on the effectiveness of the filter.

I look forward to continuing my review of this product and plan on getting some below freezing test results when the mercury starts to drop in September.

This concludes my Field Report. The Long-Term Report below are the results of the final two months of testing the Cleanstream.


Field Conditions and Performance

For the Long-Term phase of the testing I took the Cleanstream out on two more multi-day trips in addition to numerous day hikes. The conditions I used the filter in were very similar to that of the Field Report for Northern Colorado. Again, these trips sourced water from numerous water types; however since the time frame was later in the summer the water availability was limited.

This limited water availability highlighted one of the weak points of the filter, sedimentation and silt. Since the water sources were not flowing at a high rate, the water carried more sediment and debris. As mentioned in the Field Report, sediment and debris increases the amount of maintenance and "babysitting" during the filter process to unclog the filter using the back flushing method.

Even with the increased maintenance, using the gravity filter was much easier than a pump filtration system would have been; it just took more effort than it would have with cleaner water. As with previous results, the water tasted good even though a slight yellow / brown tint to the water remained.

Post trip sanitation continues to be an easy, however necessary process. I will admit that after one trip during this testing period I left the Cleanstream in the car for approximately two weeks after the backpacking outing. When I finally got the filter out of the car there was still quite a bit of moisture in the tubes and bladders as well as a funky stale odor. I was a bit worried but I ran 8 L of warm bleach water through the system and everything was back to normal.

Final Conclusion

I believe that I tested the Cleanstream fairly and under numerous conditions that will allow me to form an opinion of the Gravity Filter. I like this filter, there are places where it shines and excels and there are areas that this filter would not be my first choice. Knowing that the filter has limitation or is not well suited for certain tasks such as solo backpacking, I have not come across a filter that is more suited to treat high volumes of water. It is a good, well thought out and well made piece of gear that meets my needs when I am backpacking with my family or in a large group.

This concludes my Long-Term Report and my testing of the Platypus Cleanstream Gravity Filter. My thanks to and Platypus for allowing me the opportunity to test the Cleanstream Gravity Filter.

This report was created with the Report Writer Version 1.5 Copyright 2009. All rights reserved.

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