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Getting a CO2 Refill? Bring a Scale...

Because of how CO2 gas behaves at normal temperatures, it's impossible to look through a tank pressure gauge and tell how much CO2 is or is not, in the container. Like most common gases, CO2 has a "transition point" - where pressure crosses a line and it must remain a liquid in a steel or aluminum shell. This "transition pressure" is reached quickly and without much gas. The result is that SodaStream canisters, paintball tanks, and even traditional cylinders may be underfilled. in particular, the issue seems to be the most prevalent for our SodaStream users.

This is a table of how long a fill SodaStream container with 410g of CO2 should last in the average aquarium with the CO2ONE system. We extracted the information using tests with 20, 30, and 75-gallon tanks as references. All tanks were medium-thickly planted (so not jungles). The lighting used was "moderately high" or "high moderate" and plants (including the trickiest carpets were growing like mad). Results were achieved using the "Bazooka Diffuser", sometimes with help from a filter or Lily Pipes pipes. We maintained what looked like 20 - 30 ppm during the day. CO2 was for 8 hours as were the lights. CO2 came on half an hour before the lights and shut off half an hour before "night-time".

Tank Size

Full SodaStream Cartridge


>1 Year


9-11 Months


6 Months


3-4 Months


2 - 3 Months


6 weeks - 2 Months


1 - 2 Months

While these look pretty good, they are another unnecessary expense at the grocery store where they aren't exactly giving things away right now so a cottage industry has been developing around refilling cartridges for people like us and those that must have their flavored water.

Keep in mind that few to none of the people refilling canisters are trying to rip anyone off on purpose. They are often inexperienced and don't understand how compressed gasses work. One easy thing to do to avoid being an unwitting victim is to bring a scale! After all, CO2 has mass that can be measured, and make sure that mass is there before you leave.

Make sure it's a scale capable of at least 5 Kg for a SodaStream container and a lot larger for a full-size CGA style cylinder.

Here's a tip from our teammate Alyssa:

Like the vast majority of gas canisters, SodaStreams have their "tare weights" (empty weights) etched or fused to the metal. It often says something like "TR WT". For the vast majority of containers we have encountered, 750g seems to be the usual so make sure you have 410g of liquid CO2 for a final weight of 1160g when you leave with your canister completely full.

The tank pressure gauge that many of the new refillers are relying on does not change much at all. Even a little bit of liquid CO2 in the tank will cause it to read "full" because the rest of the CO2 is under an amount of pressure that it keeps it in the liquid state. That transition pressure can change dramatically with temperature but the tank gauge does not change much when a CO2 cylinder is 20% or 100% full. So ALWAYS BRING A SCALE! - you may be getting refills that are a fraction of how much CO2 your canister is designed for.

Unsurprisingly folks with the larger tanks reported this first because they started running empty very fast and thought there was a problem with the CO2 regulator. People with smaller tanks where refills were still months in between may have chalked it up to the system getting older and less efficient. If you make sure that your tanks are properly filled, your regulator should be as airtight and efficient as the day you plugged it in.

This is also a reason we chose a single gauge on our regulator as the tank pressure gauge does little of anything until your canister is basically empty, creating confusion among new users while being a liability that is especially likely to leak, causing the regulator to fail.

For any questions - contact us. We'd love to hear your stories!


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