Kynes studied the underarm seals, adjusted one. “Motions of the body, especially breathing,” he said, “and some osmotic action provide the pumping force.” He loosened the chest fit slightly. “Reclaimed water circulates to catchpockets from which you draw it through this tube in the clip at your neck.”

The Duke twisted his chin in and down to look at the end of the tube. “Efficient and convenient,” he said. “Good engineering.”

Kynes knelt, examined the leg seals. “Urine and feces are processed in the thigh pads,” he said, and stood up, felt the neck fitting, lifted a sectioned flap there. “In the open desert, you wear this filter across your face, this tube in the nostrils with these plugs to insure a tight fit. Breathe in through the mouth filter, out through the nose tube. With a Fremen suit in good working order, you won’t lose more than a thimbleful of moisture a day—even if you’re caught in the Great Erg.”

While the processing of urine sounds quite plausible, what does Kynes mean when he talks about faecal processing? Is it just the moisture content being reclaimed or is it something more? Also, are there male and female stillsuits?

  • 34
    No one talks about it. Do you hear me? No one talks about it.
    – John O
    Dec 19, 2012 at 18:42
  • 4
    I also suspect there was not much solid food eating done when the Fremen knew they would be going out. If they had a rotation for excursions, or even their diet in general, there may be a limit to how much solid waste they would have to deal with. I know that's what I would do... Solid waste processing, ugh. Dec 19, 2012 at 19:24
  • 7
    Imagine having a kebab with extra garlic and then going out on razzia. "Muad'dib's stench will bring the Harkonnens on us!"
    – WOPR
    Dec 19, 2012 at 22:09

5 Answers 5


To my knowledge, the mechanics of the fecal recycling is never detailed. However, it seems pretty safe to say it was the moisture content being reclaimed, as water retention is the whole point.

Presumably the solid waste was caught in a filter, and moisture pressed out over time as the wearer walked, by the motion of the legs.

And yes, there would have been male and female stillsuits, as tight fitting was essential to proper functioning.

  • 6
    I would suspect suits would be entirely custom-fit to ensure maximum efficiency. A still-suit would be a biochemical marvel by today's technological standards. Able to trap all moisture, urine, feces, process, reclaim and separate that moisture while making it possible to remove solid wastes without risk of contamination or disease? A device whose applications cannot currently be done even with all NASA has to offer. Perhaps we simply haven't had a reason to try yet. Global warming may give us a reason before too long... Dec 19, 2012 at 19:10
  • @Thaddeus I suspect proper still suits are custom fit. However, there are examples of general still suits that aren't tailored to the individual (such as the one Paul was wearing in the scene quoted in the question, iirc, as well as the ones left for Paul and Jessica during the Harkonnen attack).
    – Beofett
    Dec 19, 2012 at 19:47
  • 2
    @Thaddeus especially when you consider that its almost guaranteed that no one ever washed the suit... I'm guessing there weren't very many laundromats on Arrakis.
    – Beofett
    Dec 19, 2012 at 20:40
  • 1
    See and I hadn't even gone THERE. I forgot water was a commodity on Arrakis. Double ewwwwwww. Dec 19, 2012 at 20:49
  • 1
    I wouldn't exclude cleaning, considering you can indeed clean stuff without water, it's just the most common thing being used (due to its properties and availability). You can clean stuff with sand (they've got enough of that I guess) as well as other liquids like alcohol, weak acids, etc. - all things that won't qualify as (drink) water.
    – Mario
    Dec 21, 2012 at 12:17

The Dune Encyclopedia describes in detail how stillsuits reclaimed moisture from urine. It doesn't mention faeces, though.

However, it does have an entry on "Fremen menstruation":

From the earliest designs, stillsuits for women were constructed differently from those of the men: in addition to the thigh pads which processed urine and feces, the women's suits included a third processing unit for reclaiming the water lost in menstrual blood. In the later, even more efficient versions, these units kept female water loss on a par with that of the male, in spite of their physiological handicap.

(Note that the Encyclopedia is not canon: none of its articles were written or approved by Frank Herbert, but some of them are more convincing than others.)

  • 1
    And in another article, it says that Fremen woman don't menstruate nearly as much as women from other races.
    – Mr Lister
    Dec 20, 2012 at 8:35

While it is only implied that moisture was reclaimed (no word about reclaiming dry food) there is one significant omission in water balance of a stillsuit.

It was implied that no more than a thimble of water per day was lost. Interestingly, a body produces about half a glass of water above the balance every day.

The extra water comes from burning food. Organic matter (food) is composed primarily of various compounds of carbon, oxygen and hydrogen. The process of "burning calories" involves reaction of these with atmospheric oxygen, producing carbon dioxide and water as products of the reaction. That water comes from burning dry, dehydrated food.

Which means either the daily water loss of a stillsuit was half a glass plus a thimble, or more likely Herbert had no clue about human body water cycle and stiltsuits would actually produce extra water.

  • That water doesn't disappear though, it has to go somewhere.
    – Justin C
    Dec 20, 2012 at 15:23
  • While interesting, I don't really see a contradiction here. The water produced as a by-product can be used in a number of other ways as well as excreted or sweated out. Out of all the moisture that is released into the stillsuit, only a thimbleful is lost. The rest is reclaimed. Dec 20, 2012 at 19:08
  • @coleopterist: Yes, except you leave with the catch pockets half-empty and a week supply of food, and come back a week later without food and with catch pockets full, emptying them into the Sietch's reservoir. Something like that would be mentioned in the extreme scrutiny of water balance.
    – SF.
    Dec 21, 2012 at 0:09
  • 1
    I don't understand your argument as to why this is an error. If Herbert had said no water was lost, presumably we would interpret that to mean that 100% of the water human bodies normally give off (through sweat, urination, feces, and any other processes by which water molecules leave human bodies) was reclaimed. This might be equal to all the water we drink plus half a glass from food. So if Herbert said only a thimbleful was lost, doesn't that just mean that 100% (however many glasses that is) minus one thimble was reclaimed every day by the stillsuit?
    – Hypnosifl
    Mar 14, 2015 at 13:17
  • @Hypnosifl: Then why wasn't the effect of fremen returning from a trip with more water than they left with accounted for in the highly-detailed analysis? The descriptions imply stillsuits were lossy, if minimally so, not that they were water production devices which produced a thimble less than maximum theoretically possible per day.
    – SF.
    Mar 14, 2015 at 14:20

In book 3 they talk about the fremen colon having adapted to making the stool as dry as possible before excretion. In addition to that suits also used pumps built into the heels, and without those you just lose the water vapor. The suit encourages sweating to pull heat away from the occupant. The first layer wicks away water and the second layer uses heat and pressure to cause reverse osmosis through the 2nd layer and into the catch pockets which circulate to improve cooling between them and the desert. The urine filter is bigger to accommodate larger quantity at once and greater needs of cleaning, the stool is heated and pressed to pull away moisture for sterilization and to sterilize the dry stool for dropping. Asides from fancy materials for efficiency sake we could make this happen.

  • Can you provide any notes from the texts which support your claims? While I don’t doubt they are true, providing evidence helps those who may not have read the books to confirm your accuracy!
    – Edlothiad
    Jun 24, 2018 at 22:38

Excuse me for this, I put myself to use as Mentat. This post is long yet worthy with every portion of its parts essential.

Somewhere in part two of dune I believe I do remember a passage of the importance of water in the body while moving through the Erg, it's implied that one should drink often, but not deeply. That all moisture should be utilized.

It's also noted that the Fremen are perfectionists, it wouldn't be surprising if they would plan their own individual water allowance on a journey as per the capacity of the stillsuit and reclaim their own water back into their body cyclically throughout the excursion.

I imagine that a stillsuit is thought more as an extension, another organ, a second skin rather than explicitly as a tool to be used. Beyond the retrieval of water from the environment or held in literjons I think the water in the stillsuit would be too sacred to simply release into the reservoir, especially if the stillsuit is truly held in such reverence.

Beyond that no Fremen truly parts with the water of their body except for in death. No Fremen sacrifices their own water for those stupid enough to lose their own water. Water amongst the Fremen of the Sietch seems to only ever be shared from body to body during the tau orgy that follows the Bene Gesserit ritual of Agony or, of course, upon someone's death. Otherwise Fremen of the Sietch are only ever described either eating or with water claimed either through trade or in death, which goes to say either that particular Fremen is either quite crafty in mercantile or a bit murderous

On the whole reservoir idea, that water is being saved for terraforming, not personal use. That's why they still make good use of their own precipitation catchers, dew scrapers, and literjons.

On water balance itself. There's very little food in the desert and arid nature and white hot sun of Arrakis would likely make the water cycle much more intense, especially if we consider the fact that the night sky is reddish in hue, Arrakis is probably quite Massive if it red shifts the atmosphere. During the day Arrakis is described as having a grey haze of a sky, much like Mars does. If (assuming correlation with atmospheric density and light refraction and diffusement) knowing Mars has a thin atmosphere and also that Arrakis is massive it then the atmosphere of Arrakis is likely thin but relatively dense, dense enough to support life but thin enough to allow a lot of moisture loss by the white sun.

Also, again I can't cite the page but I remember reading that the atmosphere on Arrakis had an almost equal ratio of oxygen to hydrogen to nitrogen, with some other gases likely, maybe even spice itself. With a high amount of oxygen it would come as no surprise that evaporation occurs at a quicker rate, oxidation and what not.

So... It may just be the case that you really only lose just a thimble of water.

Beyond this, the body is in a constant state of chemical processing. Yeah, there's an extra cup of water if you do the math, but in a realistic practical setting you don't just have that sloshing around inside you unless you have to pee, but with the length of time it takes to digest food and the time frames excursions it seems unlikely that the half cup would be a present factor as the moisture in the food would still be going through electrolysis. That being said that water content mostly goes to surrounding tissues rather than going directly to the bladder or the skin, in an awful example this is why allied fighters in WW2 gave rescued peoples from the concentration camps food, however no water. Their bodies would've gone into toxic shock from the water so instead were given food to make up for lost moisture.

Done with my rant. It's still a thimble of water, and no one touches the Sietch reservoir.

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