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Reviews > Water Treatment > Filters > Platypus Cleanstream Gravity Microfilter > Test Report by Kathryn Doiron

Platypus CleanStream Gravity Water Filter

Test series by Kathryn Doiron
Initial Report: May 28, 2009

Field Report: Aug 3, 2009

Long Term Report: Oct 6, 2009

Image of Platypus filtration system
Image from Platypus website

Personal Information:
Name: Kathryn Doiron
Age: 33
Gender: Female
Height: 5' 8" (1.7 m)
Weight: 150 lb (68 kg)
Email: kdoiron 'at' gmail 'dot' com
Location: Washington DC, USA

Brief Background: I started backpacking and hiking seriously almost four years ago. Most of my miles have been logged in New Hampshire and Massachusetts. I have recently finished 1200+ miles (2000+ km) of the Appalachian Trail. My style is to be as light as possible while not spending a fortune. My pack weight tends to hover around 25 lbs (11 kg) with two days of food and 0.5 L of water. I have recently started getting into winter hiking, snowshoeing and kayaking.

Product Information:

Manufacturer: Cascade Designs/Platypus
MSRP: n/av
Weight: (stated) 13.7 oz (388 g)
Weight: (actual) 13.2 oz (374 g)
Size available: 4L sized reservoir

Weight Breakdown
ItemWeight (oz)Weight (g)
Dirty Reservoir385.5
Clean Reservoir2.778.7
Filter Unit4115.3
Filter End Cover0.051.5
Short Hose 0.515.7
Long Hose256.6

Initial Report:
May 28th, 2009

The Platypus CleanStream Gravity Water Filter is a pump-free water filtration system that is powered solely by gravity. The system doesn’t require any pre-pumping to prime. The setup consists of a ‘dirty’ reservoir and a ‘clean’ reservoir, each with either dirty or clean printed on it. A piece of tubing with a quick-connect attachment connects to the bottom of the dirty reservoir then into the filter unit. Another piece of tubing connects to the output side of the filter and has a screw in fitting to connect to the bottom of the clean reservoir. There is hose clamp on the clean tubing to stop the flow as needed. Both reservoirs are capable of holding 4 L of water, feature a webbing handle at the top and a zip opening for easy filling. Both reservoirs and the tubing are made from BPA-free materials. The quick-connect allows the dirty side of the tubing to be quickly detached and the reservoir refilled without loosing a drop of water. The reservoir can also be filled directly from the top while filtration is occurring. Website specs for the system say that 4 L can be filtered in 2.5 minutes and is 99.9999% effective with a filter pore size of 0.2 micron. The whole system comes with a storage bag that is mesh on one side and a nylon material on the other side.

Detail of the quick connect   Detail of the clean connection

My initial impressions of the whole filtration system is that is doesn't look that compact. The system does come with a stuff sack which seems large, and everything was in pieces so a little assembly is required. The assembly is pretty straight forward. I have the option of either just looking at the picture provided on the box, or the instruction manual provided opens up into a large sheet (10 x 16 in. or 25 x 40 cm) with more detailed instructions on assembly, and how to back flush the filter. The system looks very easy to use. Once assembled, the instruction sheet suggests rolling the tubing around the filter unit, stacking the two bags, then rolling the whole system together and storing in the stuff sack. They recommend not storing the filter unit with water inside, and they also recommend keeping all the tubing connected to prevent cross contamination.

The items that make up the Platypus CleanStream are softer then I expected. I am used to the older Platypus reservoirs but these ones are nice and soft. Other then the zip at the top and the connections, the reservoirs are soft and pliable. The tubing is also soft and pliable and it was easy to attach the tubing to the filter unit. Even the outside housing of the filter unit is made of a softer rubbery material, not a hard shell as I expected.

CleanStream rolled and partially stored

The filter unit is one piece. There does not seem to be any way to open the unit. Looking around on the Platypus website, I noticed that the whole unit is replaced not just an inner part of the filter. The filter can be cleaned in the field by simply backflushing clean water through the filter. This is as easy as switching the positions of the bags to let gravity do its thing. The filter can also be checked in the field by trying to blow air through the unit. If no air moves through then the unit is still good, but if bubbles appear on the other side, then the filter is bad. The filter can get air trapped inside which can slow down the operation of the filter. Simply reversing the flow of the water, blackflushing, will dislodge the trapped air and will increase the flow of filtration. The manual provided has instructions on filter maintenance. It is recommended that the filter be disinfected after long-term use (15+ days) or before and after long term storage. It is as easy as running a dilute bleach solution through the filter. The bleach will prevent bacterial and mold growth while stored.

Detail of the filter unit

On top of simply using the system as a filter unit, the clean tube can be detached from the filter unit and the water dispensed using the shut off valve. Water can also be filtered directly into a drinking system by simply removing the bite valve from the drinking hose and hooking the hose directly up to the outflow of the filter unit.

My test plan over the next couple of months will be to use the CleanStream filter on all my outdoor activities including to use the system as an in camp water source as well as dispensing directly into my hydration system. My trips will include backpacking in the George Washington National Forest and the Shenandoah National Park, plus dayhikes as well as occasionally kayak camping.

Field Report:
August 3rd 2009

I have used this filter on three overnight trips and under varying group sizes. The most was a group of about 10 people and at a dry camp, the least was just myself. Trips are detailed below.


The first trip out was a two night trip in West Virginia in the Roaring Plains with a group of 10 people. The temperatures were down to about 55 F (13 C) at night, both nights. The elevation was relatively constant at about 4000 ft (1220 m). The first night was quite late and we just set up and went to bed immediately. The next day we hiked over to the first water source and I filtered 4 L for the group. The filter was doing about 1 L a minute. That night we had a dry camp so I hiked back with someone and picked up 10 L of water for the camp. I filtered one 4 L bag, plus one Nalgene bottle (1 L) and another 1 L in my bladder. After filling the clean reservoir, I refilled the dirty reservoir, hooked up the system again and carried the whole thing back to camp. As the dirty reservoir has the quick-connect system, it doesn't leak, but the clean reservoir doesn't and requires a lid to prevent water loss. The system didn't come with a lid and as such I had to keep the system connected in order to carry the water. Back at camp, I hung the clean reservoir for anyone to self-dispense. Most people were pretty quick to figure out how it worked. I filtered the other reservoir when the first was empty and the group was good for the night. The next morning I filtered another 4 L at the stream then another 4 L at the next stream. I timed one filtering at about 3 minutes 45 seconds. The filter definitely filters faster when the air bubbles have been removed from the filter. I back-flushed the filter each time after filtering.

The next trip out was a one night trip out to the Brighton Lakes area in Utah. It was 5 mi (8 km) both days with an elevation gain of about 4500 ft (1370 m). At the higher elevations, the wind was cooling as was the snow. The filter did a great job filtering the lake water. As it was raining out, I had to bring the filter unit into the tent to filter the water. In order to get enough gravity to keep the filter going, I ended up balancing the dirty bag on my head. In spite of the limited space and height restrictions, the filter still managed to filter about 1 L per minute.

Limited space to operate.

The last trip was a three day, two night trip down at Bryce Canyon. As this was a car camping trip, the filter didn't see much use until the last day when we hiked into see Lower Calf Creek Falls. The water was nice and cool and I filtered some water for the trip back. With no trees near the waters edge, I just stood there and filtered what I needed. The filter works quickly and has no moving parts to deal with, so I have time to enjoy the scenery while waiting for the filter to work. It is easy to change positions of the bags to flush out either air bubbles (which speeds up the filtering) or to backwash the filter of sediment.

Filtering while enjoying the view.

Impressions and Comments:
So far, I have used the filter as a group filter, solo and for two. This filter is versatile and as it works with other bladder systems, I was able to fill my Platypus reservoir as well as someone else's Non-Platypus reservoir just by popping off the bite-valves. As a group system, everyone appreciated having a ready supply of water hanging from a tree. The filter does not remove tannins from water sources, so the water was still a faint brown-yellow after filtering tannic-water.

Filtered and ready for group use.

Because the system can be kept closed, it is possible to bring water to any location and filter as needed. Due to rain, I ended up filtering water inside the tent with very little dripping. I can disconnect from the dirty bag and have easy access to the clean water. The hoses do hold in some water that will leak out, but knowing that I pay attention to the hosing and where I drop it. My one beef with the filter is that the clean reservoir didn't come with a cap. I either have to leave the whole system attached to prevent accidental leaks or I have to ensure the shut off is closed tight and I would not trust that in a pack full of gear. I do have a cap from a previous bladder and have used that to allow storage of clean water in the clean reservoir in my pack. This did come in handy on one trip when the water sources were few and far apart.

Pros so far: easy to use, single or group use, and hands-free when hung. Cons so far: no cap for the clean reservoir.

Long Term Report:
October 6th 2008

I have used this filter on one more overnight trip as outlined below as well as part of my 'emergency' kit for a kayak training for a total of 6 nights use over the test period.

The last trip out was a simple overnight out in the Shenandoah National Park. This was about a 3 mi (4.8 km) hike in with an elevation loss of about 1000 ft (305 m) over 3 mi (4.8 km). Temperatures were in the mid 60's F (about 18 C) during the day and dropped to about 50 F (10 C) at night. This was a solo use for the filter system. I found the 4 L bags over kill for a one night, one person trip. I used them in spite them being too much for me and simply filtered what I actually needed.

As I currently use Platypus for my drinking reservoirs, hooking into the filter system was a snap. I have two different styles of attachment, both the snap fitting as used on the 'dirty' reservoir and the regular screw fitting as used on the 'clean' reservoir. As I have these in the 2 L sizes, I feel I can easily turn this filter system into a one person system simply by swapping out the 4 L reservoirs for the smaller 2 L reservoirs. I love that versatility of the system. Not only can I use it for personal use, but it is great for group use. The filter and reservoirs are a snap to clean out both in the field and at home. In the field a simple back flushing cleans and declogs, while a mild bleach solution sanitizes the filter for storage. I do feel that the system should come with a cap for the clean reservoir to use as a water storage reservoir. Currently it is not supplied with a cap.

With the amount of use I have had from the filter system, I have not come close to the maximum number of liters that the filter can handle. I have not yet had a chance to see how the filter behaves as it nears the end of its filtering capacity. There is nothing on the filter to indicate when it is done, but there are clues such as slower flow rate and bubbles. I will continue to keep an eye out for these clues. This has been a great filter in my opinion and I can see this becoming a part of my kit, especially for group trips.



This concludes my long term report on the Platypus CleanStream Gravity Water Filter. I hope you have enjoyed reading this test series and found this report valuable. I wish to thank and Cascade Designs/Platypus for allowing me to test this filter.

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Read more gear reviews by Kathryn Doiron

Reviews > Water Treatment > Filters > Platypus Cleanstream Gravity Microfilter > Test Report by Kathryn Doiron

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