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GravityWorks 4.0L Filter System

4.378787878787879 out of 5 stars
132 Reviews
Color:One Color



Why We Like The GravityWorks 4.0L Filter System

The GravityWorks 4.0L Filter System is pretty dang easy to operate, and there are plenty of devotees who can't get enough of the world's simplest water filtration system. Just fill one of the Platy Zip bags with water, place it above the empty bag, open the hose clamp, and let gravity do the rest. In 2.5 minutes, you'll have four liters of clean water, and if camp is far away, fill the other bag to carry back with you. Open the hose clamp to dispense water, and shut it to stop the flow. To clean, simply reverse the bags for four seconds, running water through the filter in reverse. That's seriously it.


  • Gravity filtration system ensures effortless filtering while backpacking
  • Two 2L bags for dirty water suspended over one another for auto filtration
  • Filters 4L in 2.5 minutes without any need for pumping
  • Shut-off valve eases control when filling up water bottles
  • Reverse-flush cleaning takes four seconds
  • Item #CAS001G
Purifying Element
hollow fiber
protozoa, bacteria, particulate, giardia, cryptosporidia, E. Coli, salmonella, cholera
hollow fiber
Pore Size
0.2 microns
Cartridge Life
4L / 2.5min
Field Cleanable
yes, backflush
3 x 9.5in
Claimed Weight
Manufacturer Warranty

Overall Rating

4.5 based on 132 ratings

Review Summary

1 Stars - 8 reviews
2 Stars - 5 reviews
3 Stars - 8 reviews
4 Stars - 19 reviews
5 Stars - 92 reviews

Fits True To Size

Screen reader users: the following list provides a visual scale to illustrate the product fit. Please refer to the heading above for the fit type in text.
Runs smallTrue to sizeRuns large

What do you think about this product?


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3 out of 5 stars

November 18, 2023

Questionable reliability

I purchased a 4.0L Gravityworks filter back in 2022 and was initially exceptionally pleased with it. Used it the summer of 2022 and was quite happy with the results. I followed the instructions to a “tee” at the end of the season when putting away for long term storage. When I pulled it out May/2023 I didn’t test it beforehand (I should have, that’s my fault). But I hiked up into the bush and when I got to the camping area I went to get my water. I filled the dirty reservoir, and made all the necessary attachments to the clean bag. Zero flow. None. The water wasn’t penetrating the filter at all. I was mortified at the catastrophic gear failure. I always backflushed, had used the filter only sparingly and, as mentioned, followed all instructions for long term storage. So I was forced to boil water for my drinking and cooking needs. Not an ideal situation, particularly since I’d only brought so much fuel. I was able to boil enough water for my needs for two nights in the bush but it was a labour intensive undertaking that should have been avoided but for a clogged filter. After that trip I purchased a replacement filter and took it on a six day solo hike of the North Coast Trail. On night one it worked like a charm. Super fast flow and I had eight liters of water in about 10 minutes. During the trip I always made sure to back flush after every other filter. Nevertheless by my last day the filtering process took considerably longer than that first day. Eight liters was taking me about 30-45 minutes to filter. I’ve just stored the filter away for the winter (per instructions ) and will test it again before my first hike in spring 2024. I want to like this filter, I really do. When it works it works well, it’s lightweight, simple to use and takes up remarkably little space in the backpack. But my experience to date has made me nervous to rely on it, particularly during multi day through treks. As such I believe my experience to date warrants a three star rating.

a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

1 out of 5 stars

November 10, 2023

Looks like it could be a great filter, but mine doesn't work (details below)

I picked this up a couple months ago thinking it would be great for canoe camping. Unfortunately there must be something wrong with the unit I received. I can barely get a trickle of flow through. I tried all the backflushing tricks that are suggested in case the issue was air bubbles trapped in the filter, but only got a trickle of flow on the backflush too. I also did the filter integrity test but I wasn't able to see bubbles coming out so I know that isn't the problem. And of course it's brand new so it can't be from sediment build up. And it's been on a shelf in my closet so no drops/freezing. Finally after fiddling with it for an hour I took the end caps off the filter to see if there was visible damage to the hollow fibers. There isn't (as far as I can tell) however there is a film (almost like glue) covering the end with all the little hollow fiber tubes. I don't know if that film/glue is supposed to be there, but in my case it seems to be blocking all water flow through the filter. Barely any water makes it through that film. Anyways, all that is to say that my filter doesn't work. And unfortunately I lost my receipt so return/warranty isn't an option. Now I have to decide if I by a replacement, or just go to another brand. I definitely don't want this to happen again given how much the filters cost.

a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

5 out of 5 stars

November 8, 2023

Great Inline Gravity Filter

This is the first gravity filter system I've owned. I owned pump filters in the past. This purchase was long overdue as it is a tremendous time saver. I've used other people's gravity filters such as Katadyn. I chose this system over Katadyn because of the in line filter. I could use it to suck water out of cracks in rocks if needed which helps bridge the gap in functionality between pump and gravity filters. The only downsides I see to the inline filter over the in bag filter like Katadyn is that it is easier to clean and visually inspect for contamination/clogging with the Katadyn filters. This being an enclosed filter, it is harder to dry out. I often camp in below freezing conditions which can destroy a filter if water freezes in the filter. If and when this happens, I would get a Katadyn filter for winter camping and use the GravityWorks filter the rest of the time. I use alum powder for silty water and it keeps the filter running smoothly.

Justin E.
a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

5 out of 5 stars

October 30, 2023

Appalachian Trail 2017

I used my 3 stage filter, from Georgia to Maine…5 months 3 days. It never failed me. After the trip, I asked my nephew what his favorite piece of equipment was on our trip…he laughed and said, “YOUR Platypus” he only had the Soyer squeeze. I’ve continue to use it for 6 years.….new filter of course.

Uncle P.
a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

5 out of 5 stars

October 19, 2023

The filtration system works great.

The filtration system works great. I use it when out for solo trips as well as group trips. Will always be my goto sytem when out for more than day trips.

Joe E.
a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

5 out of 5 stars

August 17, 2023

Makes Life Better

Our annual 1 week backcountry canoe trips (4-6 dads and up to a dozen kids) are without question made better by the Platypus (we have 2 on the trips - the larger 4L & a 2L). They are simple, beautifully mechanical, and do what they are supposed to. Having drinkable water always on the go on our busy sites is a whole different experience now that pills and pumps have been replaced by the superior gravity feed. In particular like the simplicity of the hose/tube system - friction fit stock tubing and cleanly separate components takes away concerns of mechanical connection failure. Sure there is some theatrics in pulling and re-attaching hoses for filling your water bottle - but that is in the fine tradition of simple, do-it-yourself fireside ingenuity. Well done!

a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

5 out of 5 stars

August 16, 2023

Best filter I've found

These things are so easy to use and trouble-free to maintain/clean, that I cannot imagine a better system. For the canoe tripping we do, we can let the water filter itself while we busy ourselves with more enjoyable pursuits. The chemical and pump systems I have used are a thing of the past and I won't be going back! I've had one of these for years, and am well pleased with the performance and longevity of every part of it.

a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

1 out of 5 stars

August 10, 2023


Great idea, faulty execution! Used it now on many trips (only because of the initial investment). Filters are now incredibly expensive and last a day!!!! If your water source is NOT clean. Yes, in the outdoors you will NOT always find clean water; how about that!!!! Filter clogs up, no backflushing does NOT help, and you are trapped!!!! Why they have NOT designed a cheap disposable pre-filter system is beyond me. Do not rely on it as your only source. You will regret it!

a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

1 out of 5 stars

August 6, 2023

Very dissatisfied

Purchased 4L gravity works filtration system for a backing trip. On day one of the trip I put water in the dirty water bag then hooked up the tubes to start the filtration process but water would not flow out of the dirty water bag. I unattached/reattached tubing several times but to no avail. Tried many other things to get it to work. Had to end backing trip early because could not get clean water. VERY unhappy with your product.

Chad J.
a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site

5 out of 5 stars

July 18, 2023

GravityWorks™ 4.0L Water Filter System Review

The GravityWorks Water Filter works great! I just finished a multi-day canoe trip and this system served 6 people with no problem. The only issue I encountered was when the air got into the line and I had to reverse-feed the water to remove air pockets and improve filtration speed. Great product and would definitely recommend.

Jacob D.
a Cascade Designs brand site

Originally reviewed on a Cascade Designs brand site