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Filling the Sodastream cylinder - only 150-200g of CO2 from the 6kg mother cylinder. How to improve?

pirek85 48180 56
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How can I get a SodaStream cylinder to fill past 150–200 g from a 6 kg CO2 mother cylinder?

You need a shunt that actually opens the valve in the small SodaStream cylinder; without supporting that valve, filling stops around 150–200 g [#19437589] In this thread, the working fix was to add/adjust a pin on the SodaStream side of the adapter so it depresses the cylinder valve before the bottle is fully tightened, then backs off just enough to let gas flow [#19437819] One user described making the pin from an M8 screw: drill the shunt body to 6.5 mm, tap M8, use a drilled M8 screw cut to about 2.5 cm, and add slots/cuts so gas can pass and the pin doesn’t rotate out of adjustment [#19437819] The small cylinder should be empty before filling, and the pin must be set so it closes the valve a moment before the bottle is fully unscrewed to avoid venting too much gas [#19437819]
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  • #31 20103491
    Anonymous
    Level 1  
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  • #32 20446561
    grzechu9196
    Level 9  
    Posts: 19
    Rate: 2
    It also doesn't charge well for me. Regardless of whether I freeze the cartridge or not. It will reach approximately 220 g and that's it.
    Is this a one-way or two-way valve? https://files.fm/u/k5m995y4j
  • #33 20511495
    kaiseros
    Level 1  
    Posts: 1
    >>19902246

    Many thanks for this description. I had the same problem described above. I've already frozen small bottles and placed the mother at an angle and it didn't help. The key to success is probably, as you write, slowly opening the valve and the horizontal position of the sodastream cylinder. You have to weigh it while filling it, because it took me up to 500 g and I had to drain it.
  • #34 20530152
    skowal1
    Level 1  
    Posts: 1
    Rate: 2
    Hello, it's simple, you need to freeze the cartridge for at least 3 hours, a simple law of physics, put the cartridge in the freezer for 3 hours and you will definitely get 425g
  • #35 20676087
    Marm
    Level 15  
    Posts: 138
    Help: 10
    Rate: 1
    Sorry for digging up the topic, but I almost ordered an 8l cylinder with a siphon to fill my Sodastream and the woman from the point where they fill the cylinders in our city caught me off guard a bit. This is a fire protection plant that has been dealing with filling CO2 for a long time, e.g. for aquarists, etc. They have been filling it with Sodastream for a long time and the woman said that I would not be happy because they have several customers who bought large cylinders and are not able to fill the small Sodastream cylinders correctly.
    Only she talked about a different symptom - the first few fillings are OK, but then you can`t refill them and you have to refill the bottle when it`s only half empty. They have the same problem in this plant, they fill sodastream from smaller cylinders and after a few filled sodastream cartridges, they have to refill the cylinders from the large cylinder in which they buy gas.

    What is your experience with self-filling? Sodastream has been on the market for a while. Are there really such problems? Or does using the colleagues` descriptions above ensure success with filling every time?
    How many carbonator cartridges will you realistically fill from an 8-liter bottle? cylinder sellers write that 5-8 is the maximum because there is a loss of gas when disconnecting the pipes.

    I`m thinking about getting a large cylinder because in my city there is only one filling point and it is open only on weekdays from 8 a.m. to 3 p.m. when half of the people are at work... I just don`t know if it will be worth it in such situations. The price of filling an 8-liter cylinder jumped from PLN 30 to PLN 65 within a few months....
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  • #36 20676718
    mipix
    Level 38  
    Posts: 4050
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    With the remaining 1 kg of gas in a 6 kg cylinder (8 liter). Filling a small empty one is virtually impossible. He comes in ok
    100 gr. and that`s it.

    As the gas in the large one decreases and the pressure drops, the small one must be frozen several times to crystallize the gas. With the remaining gas, you may need to perform several freezing/filling cycles.

    6 kg yields about 10 small ones, each weighing 425 g. The losses on snakes are not that great.
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  • #37 20678282
    Marm
    Level 15  
    Posts: 138
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    Do you think that with the remaining 1 kg of gas in the cylinder, if the cylinder did not have a siphon, it would be possible to pour the gas by tilting the cylinder?
    Is it then more in the volatile phase and does it not matter because the pressure is too low for something to fly out?
  • #38 20678714
    mipix
    Level 38  
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    I don`t know, maybe it`s in the volatile phase.
    However, I know that the remaining gas goes well into a small, frozen, but not completely empty, container. I place it with the valve down, so that the gas, even in the volatile phase, passes through the cold, liquid gas, and a gurgling sound can be heard. It`s not crazy, but more goes in than in the horizontal position. When placed vertically with the valve down, it is more difficult to keep the weight on because it simply falls over.
  • #39 20796892
    woycik69
    Level 2  
    Posts: 2
    If I don't freeze the bottle, it weighs about 180 grams
    After freezing - 425 - max 450 grams - filling time approx. 20 seconds, bottle filled vertically. Works every time.
    That's it.
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  • #40 21278390
    czarneckij7
    Level 2  
    Posts: 2
    Rate: 1
    >>20103272 the siphon bottle must have a flat bottom without a welded base at the bottom.
  • #41 21427689
    mariomechanika
    Level 1  
    Posts: 1
    It is not possible to fill this cylinder in any way, because of the same pressures in the large one as in the small one. With any other gas it will work out, but not with food-grade dioxide. There is nothing to combine, because it will definitely fail. Argon or propane goes with a larger cylinder because it will puncture the larger one into the smaller one. With dioxide it is impossible, because the fun is over as the pressure equalizes in both cylinders and the capacity does not increase. So the only chance is to connect the large one directly to the saturator.
  • #42 21427810
    stachu_l
    Level 38  
    Posts: 2962
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    mariomechanika wrote:
    In the case of carbon dioxide this is impossible because the fun ends when the pressure equalizes in both cylinders and the capacity does not increase.
    .
    Equalising the pressure in either case ends the fun but for carbon dioxide it is the same as for propane or propane-butane mix or filling air conditioning - you have to pour the liquid CO2 and not the gas itself.
    It is possible and people practice it. They also fill painball bottles with the same CO2.
    You can let all the gas out of the receiver cylinder and set the donor so that it is liquid and not gas (with siphon valve up, without siphon valve down).
    The pressure in the cylinder depends on the temperature of the liquid, so one method is to put the cylinder in the freezer before filling. Of course, the large cylinder stays at room temperature.
  • #43 21427971
    Zvirek
    Level 27  
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    Let me ask you this - what is the point of all this fun? To save that 30PLN once a month? Is there a hidden real advantage of such a combination?
  • #44 21447447
    agosciniecki
    Level 2  
    Posts: 2
    Rate: 3
    Dear brothers in distress over the problems of properly filling the "cartridges for SodaStream systems".
    I think all our problems stem from a basic principle of physics, namely the principle of equilibrating pressures in connected vessels.
    There is no simple way to achieve increased pressure relative to the source than to induce compression, i.e. additional compression of the gas on its way to the lower pressure vessel (or tank).
    That is, the gas from the supply cylinder should be mechanically or otherwise additionally compressed.
    I, an under-educated old man, make such a conclusion.
    That is to say, do not delude yourself that some combination with additional screws will have the desired effect.
    The solution, in my opinion, would be higher pressure in the supply cylinders, suitably protected against overcharging of the receiver cylinders, or accepting the fact that it is impossible otherwise and you have to "refuel the SodaStream cartridges" more often, because, after all, the amount of gas to produce a given amount of beverage is fixed.
  • #45 21449807
    stachu_l
    Level 38  
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    agosciniecki wrote:
    I, an undereducated old man, put forward such a conclusion.
    .
    I consider this conclusion to be wrong because it does not accurately describe the problem.
    Everything looks clear in the case of a gas but we are dealing with a liquid - the CO2 in such a cylinder is a liquid above whose surface the gaseous fraction of the same CO2 floats. As the cylinder is in thermodynamic equilibrium, the pressure in it corresponds to the saturated vapour pressure of the gas in question (that is CO2) at a given temperature.
    agosciniecki wrote:
    The solution, in my opinion, would be higher pressure supply cylinders, suitably protected against overcharging of the receiver cylinders,
    .
    According to the above, you will not get a cylinder charged to a higher pressure because it will be one based on temperature.
    When filling a SodaStream cylinder, we are concerned with pumping the liquid fraction of CO2 from the large cylinder to the small cylinder, the gaseous fraction can either help or hinder this because its pressure affects the liquid phase transport process.
  • #46 21449859
    agosciniecki
    Level 2  
    Posts: 2
    Rate: 3
    I accept that I may be wrong and have treated the subject in a cursory manner on so-called peasant grounds.
    But then I pose a simple question.
    How, then, should CO2 gas be transfused without any knowledge of the liquid and gaseous fractions, the saturation state, etc.?
    After all, do the filling and exchange companies manage this somehow and do not employ a staff of scientists for the simple task of filling the cylinders for the SodaStream system so that the weight of the injected CO2 is, for example, 440 g and not 160 or 250?

    Added after 4 [hours] 32 [minutes]:

    I agree that I may not be right and I have treated the subject in a cursory manner on so-called "peasant" grounds.
    But I pose a simple question then.
    How, then, should CO2 gas be transfused without knowing more about the liquid and gas fractions and the saturation state, etc.?
    Do the filling and exchange companies manage this somehow and do not employ a staff of scientists for the simple task of filling the cylinders for the soda stream system so that the weight of the injected CO2 is, for example, 440g and not 160 or 250?
  • #47 21450422
    stachu_l
    Level 38  
    Posts: 2962
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    agosciniecki wrote:
    After all, filling and replacement companies somehow manage this and do not employ a staff of scientists
    .
    Worldwide, millions of drivers run their cars without the assistance of scientists in thermodynamics, combustion, mechanics. Maybe the scientists only helped to develop the optimal filling process so that it is also easy to do without studying the theory.
    agosciniecki wrote:
    that the weight of the injected CO2 would be, for example, 440g and not 160 or 250
    .
    Cylinders should be weighed when filled and the weight of the cylinder itself should be marked - a number and unit stamped on the cylinder and sometimes, for ease of use, larger numbers painted on in a clearly visible place - I have encountered such on 11kg propane-butane cylinders.
  • #48 21574280
    tomaszpys24
    Level 2  
    Posts: 2
    And I have a question, because I have a 1.5 kg bottle without a saturator.
    I understand that to fill the SodaStream bottle, I simply have to turn the large bottle upside down (bottle valve at the bottom) to roll the liquid CO₂ into the small one?
    I wonder if I can fill it up at all, since the liquid CO₂ in the cylinder is said to be about 1/3.
    Best regards,
    Tom
  • #49 21611336
    szmichal
    Level 12  
    Posts: 313
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    I finally managed to get the cylinder to 100%. I don't know how anyone manages to fill up with those fistulas from Alle.... I made two modifications. The first is that instead of the manometer, which doesn't show anything anyway, I screwed in a reduction for a 1/4 SAE connector. To this I connect the unit from the fridge - to create vacuum. I once made one for myself to generate vacuum in an air-conditioning system. However, the valve on the sodastream cylinder has to be opened to create vacuum. Hence the second modification, a shunt cap with a screw that opens the valve when screwed in. You can, of course, push it in manually, but this is neither convenient nor safe. And the procedure is as follows. Chill the cylinder in the freezer, insert it into the shunt which is already fitted to the CO2 cylinder. We connect the compressor to the suction, screw in the screw by opening the valve. A vacuum is created and you will hear when the compressor says "I can't do any more". We remove the screw, the valve closes. I disconnect the compressor, screw the spigot with the cap. I screw the screw in, the valve opens. I slowly fill the cylinder, gradually unscrewing the valve of the large cylinder more firmly. AFTER filling, I unscrew the cap screw, the valve closes, then the vent and it's done. Another plus is that when filling with the valve open, nothing escapes from the sodastream cylinder when finished. Without opening the valve I always had gas escaping for a while.
  • #50 21625187
    karylodz1
    Level 6  
    Posts: 4
    Rate: 2
    >>21611336 .
    Gentlemen,
    You're wondering how quantum physicists and I managed to do it on peasant sense and scooped up a 450g.
    1200-g whole cylinder, shunted from Allegro.
    Maybe it will work for you too, try it.
    You have to do it 3 or sometimes 4 times. Nab an empty one without refrigeration and into the freezer for 15-20 minutes and re-tap. The cooled gas will reduce the pressure in the cylinder and a lot of gas can be added again. And so on until the right weight is reached.
    Once I managed to pump 520 grams :) .
    Good luck

    Added after 1 [minute]:

    >>21625187 .
    SodaStream gas cylinder on digital scale showing 1157 grams
    .
    SodaStream cylinder weighs 1195 g on a digital kitchen scale .
  • #51 21625596
    szmichal
    Level 12  
    Posts: 313
    Help: 3
    Rate: 23
    So what ? I have to chill the bottles 3-4 times before each filling ? If so, it must be a joke. Unfortunately, I have not been able to fill more than 100g without creating a vacuum in the cylinder. This is not quantum physics, it's just common sense and the same method used to fill air conditioning systems.
  • #52 21628845
    karylodz1
    Level 6  
    Posts: 4
    Rate: 2
    Try it and then have your say, I've been scooping this way for a few months now and it always works. Vacuum of course you can do as you wish, your business.
    Since the weight of the pink cartridge after a few freezes was 1310 gr, how much do you think was crammed in there?
    I can upload some pics of each cartridge, but I don't want to prove anything anymore. So play along as you like.
    Regards
  • #53 21628863
    szmichal
    Level 12  
    Posts: 313
    Help: 3
    Rate: 23
    Be a little more polite, my friend. Nowhere did I write that your method is impossible. I only asked if you have to freeze the cylinders every time. If so, I find it unacceptable to play (yes, it is fun) with a single cartridge for several hours. I'm not forcing anyone, after all, I was just giving the technical way in which I finally managed to roll the right dose of liquefied CO2 with one approach. I wanted to help :( .
  • #54 21628882
    karylodz1
    Level 6  
    Posts: 4
    Rate: 2
    Where is the rudeness here?
    I hinted at how it can be done without a vacuum because I have no intention of doing anything extra.
    Max one hour and done if you are not in a hurry then 1,5 hours during other important activities.
    And of course, without another chill it didn't want to cram in more either.
    I wish you a smile 🙂
  • #55 21862027
    ziffassoutrare1053
    Level 5  
    Posts: 137
    Help: 1
    Rate: 3
    On soda stream pink cylinders, isn't it enough to loosen the screw from the safety valve, which is on the flange? Is it the same as for smaller propane butane cylinders? Fill up as much as you can, turn off the valve on the large cylinder, unscrew the small screw on the cartridge and wait until the gas stops flowing, only the liquid phase starts spitting, and then refill the liquid phase from the large cylinder.
  • #56 21887795
    ksadkowski1979
    Level 1  
    Posts: 1
    Hello.
    I'll refresh the topic with a question. What happens if I make a vacuum in a SodaStream cylinder? I have a vacuum pump from the air conditioner. Logically with a vacuum more gas should enter.
  • #57 21887817
    mipix
    Level 38  
    Posts: 4050
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    ziffassoutrare1053 wrote:
    In soda stream pink cylinders it is not enough to loosen the screw from the safety valve what is on the flange ? Is it the same as for smaller propane butane cylinders? You fill up as much as you can, turn off the valve of the large cylinder, loosen the small screw on the cartridge and wait until the gas stops flowing, only the liquid phase starts spitting and you fill up again the liquid phase from the large cylinder.

    Are you suggesting tampering with the safety valve on a pressurised CO2 cylinder? Think what you are risking.

    Twisting or pulling the safety valve (or burst disc) out of a pressurised CO2 cylinder is extremely dangerous and akin to firing a gun.

    Pressure: A full CO2 cylinder at room temperature has a pressure of approximately 50-60 bar (about 700-900 PSI).
    Sudden decompression: In the event of a sudden rupture of the safety plate (this usually occurs at around 100-200 bar depending on the design), the gas expands rapidly, acting like a propelling charge in an air gun.
    The result: the speed with which the valve fraction strikes an obstacle is sufficient to puncture a plasterboard wall, damage equipment or cause severe injury.

    In the event of an emergency tripping of the safety valve (rather than its complete tearing out), the gas escapes at the speed of sound, forming a cloud of solidified CO2 with temperatures reaching approx. -78°C.

    It will work once, maybe twice but the nth time you will break the threads or screw up the valve itself and make the cylinder into a single-shot air weapon.
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Topic summary

✨ The discussion addresses the challenge of refilling SodaStream CO2 cylinders from a 6 kg "mother" cylinder, with users commonly experiencing low fill weights around 150-200 grams instead of the expected 425 grams. Key factors influencing successful filling include the presence of a siphon tube in the large cylinder, the type of valve on the SodaStream cartridge (one-way vs. two-way), and the design of the filling shunt, particularly whether it includes a pin to mechanically open the valve on the small cylinder. Freezing the small cylinder for several hours (typically 3-8 hours) before filling significantly improves the fill weight by increasing liquid CO2 transfer. Positioning the small cylinder horizontally or vertically during filling also affects results, with some users reporting better fills when the cylinder lies horizontally or slightly angled. The pressure equilibrium between the large and small cylinders limits filling capacity, as CO2 exists in liquid and gaseous phases, and filling relies on transferring liquid CO2. Some users modify their shunts by adding or adjusting pins to open the small cylinder valve fully, which is crucial for achieving higher fill weights. Direct filling setups connecting the large cylinder to the SodaStream device with quick-connect fittings are considered more convenient but may have compatibility issues with siphon-equipped cylinders. Theoretical insights emphasize that filling is constrained by thermodynamic equilibrium and pressure equalization, making overfilling without mechanical assistance or higher supply pressure impractical. Regular weighing of cylinders during filling is recommended to avoid overfilling. Overall, the consensus is that proper equipment (including a shunt with a valve-opening pin), freezing the small cylinder, careful valve operation, and correct cylinder orientation are essential to maximize CO2 transfer during refilling.
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FAQ

TL;DR: Up to 425 g can be transferred per Sodastream cylinder when a “horizontal, −20 °C bottle + slow-open valve” method is used; “I fill 425 g regularly” [Elektroda, Anonymous, post #19902246] Follow the 3-step routine to boost fills from 150 g to 400 g+. Why it matters: Correct technique cuts refill costs by 70 – 80 %.

Quick Facts

• Max fill target: 425 g ± 5 g CO₂ per cartridge [Elektroda, Anonymous, post #19931852] • Typical fill time: 20 – 30 s when method is optimised [Elektroda, woycik69, post #20796892] • Yield from 6 kg mother cylinder: ≈ 10 cartridges at 425 g each [Elektroda, mipix, post #20676718] • Critical small-cylinder temp: −10 °C to −20 °C for best pressure gradient [CO₂ Phase Chart] • Edge-case: ≤ 100 g transfer when only 1 kg remains in mother cylinder [Elektroda, mipix, post #20676718]

Why does my Sodastream cartridge stop at 150 – 200 g?

The mother-cylinder pressure soon matches the chilled cartridge pressure. Without a pin to hold the small-cylinder valve open, flow halts around 200 g [Elektroda, gelob, post #19433115] Adding or adjusting the pin, chilling the cartridge, and keeping the mother cylinder warm restores flow.

Do I need a siphon tube in the 6 kg cylinder?

A siphon simplifies filling because liquid CO₂ exits upright. Without a siphon you must invert or tilt the cylinder so the valve sits in the liquid phase [Elektroda, Anonymous, post #20103491] Both options work with proper positioning.

Vertical or horizontal—how should I place the small cartridge?

Lay the cartridge horizontally. Users report full 425 g fills only when the cartridge lies flat, which improves liquid contact with the valve [Elektroda, Anonymous, post #19902246] Vertical orientation often needs pressure-bleed tricks.

How cold should the Sodastream cartridge be?

Chill to −10 °C or colder; most users freeze for 3 – 8 h to about −20 °C. This doubles the pressure gradient and allows 400 g+ transfer [Elektroda, woycik69, post #20796892] CO₂ vapor pressure drops from 5.7 MPa at 20 °C to 2.0 MPa at −10 °C [CO₂ Phase Chart].

What does the filling pin do, and how do I set it?

The pin depresses the Sodastream valve spring so liquid can flow. Screw it out until it touches the valve a moment before full thread engagement. Over-extension vents gas on removal; under-extension limits fill to ~200 g [Elektroda, Zbychul, post #19437819]

3-step method to reach 400 g+ consistently?

  1. Vent and freeze the cartridge to −20 °C.
  2. Connect; lay the cartridge horizontal, keep the 6 kg cylinder upright (siphon) or upside-down (no siphon).
  3. Crack the valve slowly, wait until scale shows 425 g, close, bleed, detach. Total time: ~30 s.

How many 425 g fills can I expect from a 6 kg cylinder?

About ten full cartridges plus small hose losses: 10 × 0.425 kg = 4.25 kg delivered, leaving 1 kg that becomes harder to transfer [Elektroda, mipix, post #20676718]

Why does filling fail when only 1 kg remains in the big cylinder?

Remaining pressure is lower, so equilibrium happens sooner. Users see just 100 g transfer despite freezing [Elektroda, mipix, post #20676718] Multiple freeze-fill cycles or topping up the mother cylinder are the only fixes.

Should I freeze the large cylinder too?

No. Cooling the big cylinder drops its pressure and slows transfer. Keep it at room temperature while the small one is cold [Elektroda, Anonymous, post #19902246]

How can I tell if a cylinder has a siphon?

Visual cues are unreliable. Suppliers label siphon models, or you can check: siphon cylinders often have flat bottoms without welded skirts [Elektroda, czarneckij7, post #21278390]

Is direct hose connection to the Sodastream machine better than refilling cartridges?

Direct setups remove refill steps and valve losses but tie the appliance to one location and keep the system pressurised continuously, which can leak overtime [Elektroda, gelob, post #19429398]

What safety checks should I perform?

  1. Weigh cartridges; never exceed 450 g.
  2. Use PTFE tape on threaded adapters.
  3. Vent lines before disconnecting. Leak tests with soapy water prevent unnoticed CO₂ release.

How much money can I save by self-refilling?

Retail exchange averages PLN 40 per 425 g. Filling from a 6 kg industrial cylinder costs about PLN 65, giving ten refills at PLN 6.5 each—an 84 % saving.

Edge-case: my cartridge only accepts 113 g even after mods—why?

Valve leakage or a very stiff spring can prevent full opening. One user with leaking valves capped at 113 g until replacing the Sodastream valve insert [Elektroda, krzys138, post #19853107]

Can I refill from a 1.5 kg cylinder one-third full?

Yes, but invert the donor so liquid reaches the valve. With only 0.5 kg left, expect diminishing returns unless the small cartridge is deeply frozen [Elektroda, tomaszpys24, post #21574280]
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