CO2 Adapter
Filling Process
Gas Quality
Gas Bottles
CO2 Cylinder


– Filling of CO2 cylinders

The filling of the CO2 cylinder is done by pressure equalization between the large gas bottle and the small cylinder. The “liquid” CO2 is transported out of the bottle into the small cartridge. Given both gas tank and the CO2 adapter are connected. Turning up the hand wheel of the large gas bottle, the valve of the cylinder opens and liquid CO2 flows and the pressure is compensated in the cartridge. After about 20-25 seconds, both containers have the same pressure and the cylinder is, as documented,fully filled with liquid CO2.

Carbon dioxide gas is transported in cylinders and sold in liquid form. CO2 has the property that it remains liquid under pressure and always flows downwards or settles at the bottom of the bottle. In the upper part of the bottle CO2 is gaseous.

When you connect a gas bottle “without a dip tube valve” to the cylinder and open the valve, it then transfers only gaseous CO2. The cylinder is not full with about 30-40gr gaseous CO2. If the large gas bottle is, however, reversed before the opening of the valve, then the liquid CO2 flows downward and is in front of the valve stub. As soon as the handwheel is opened, only the liquid CO2 flows into the cylinder. The cartridge is filled with liquid CO2.

A gas bottle with a dip tube valve, the principle is the same. The difference is, that bottles with this valve does not need to be turned. The valve connector is extended over a so-called syphon tube to the bottom of the bottle. Therefore, the valve is permanently at the bottom of the bottle liquid phase. When opening the valve only liquid CO2 leaves the gas bottle.

If you have a gas bottle without a dip tube valve, this has to be reversed before opening or be “upside down”.

A gas bottle with a dip tube valve can remain normal for decanting.

There are basically 2 ways to fill the cylinder:

  1. The filling of a non pre-cooled cylinder. A max. 250-300gr can be filled in the cylinder.
  2. If the cylinder is placed in the freezer 1-2 hours prior to filling, then you can fill the cylinder completely.

The level can only be determined primarily. CO2 is measured in grams or kilograms / (Pound (lb). The pressure in carbon dioxide gas cylinders is constant even when decreasing. Therefore, the load capacity can not be determined via the residual pressure.

The filling process is complete after about 20 – 25 seconds and the pressure equalized. The flow of gas is then inaudible and the cylinder is full.

Due to pressure equalization gas no longer flows even when the valve is open.

The valve therefore does not need to be closed at exactly 30 seconds, but can also, for example be turned off after 1 minute.

The capacity depends on the temperature of the gas container.

With warmer bottles pressure rises and the final amount is increased slightly.
Conversely, when the large gas bottle is very cold, the tank pressure decreases reducing the capacity.

For the best results, get a gas bottle with room temperature (18-20°C / 65-68°F) and a pre-cooled cylinder.

When the cylinder receives temporarily more than 425gr CO2 so that’s no problem. A higher capacity resulting from the combination of a pre-cooled cylinder and a more than 20°C / (68°F) warm gas bottle. The cylinder could work with this amount, however, the force increases for valve operation. Protect the water bubbler and work with the provided amount of 425gr.

No. Overfilling is impossible due to the pressure equalization. CO2 cylinders and gas bottles are designed for the same operating pressure and work regardless of the bottle size. The pressure in the larger bottle is determined only by the temperature and can not rise while filling. After filling the two gas containers have the same pressure.

Often, it is assumed that the pressure in large gas bottle is higher than in small cylinders. However, this is not true for CO2 gas.

At 18-20°C/ (65-68°F) room temperature small cylinders and large gas cylinders have an identical cylinder pressure from 60-65bar.

(Pressure relief valves protects the body an approved bottle by up to 250 bar of.)

Even with decreasing level, almost to the depleted CO2, the pressure remains constant for temperature. The large gas cylinders can therefore be almost completely used up (to about 1 kg / 2 lbs). Theoretically, the residual amount could also be taken. However, once the liquid level drops below the valve stub or in the standpipe bottles below the immersion tube, gaseous CO2 is only detected.

– General questions

This is of course dependent on the size of the bottle used.

A gas bottle with 22 lbs (10KG) CO2 content is about 20 cylinder fillings á 425gr.

The contents of the large gas bottle can be use up almost completely.

See the selection in “questions” for a checklist for “troubleshooting”.


Pressure reducing devices must not be used during filling.

Pressure reducers are designed only to regulate the pressure of gaseous CO2.

Filling must only be done outdoors.

CO2 is not combustible and a relatively harmless gas. In enclosed spaces it can be harmful if high concentrations are reached. Carbon dioxide is also colorless and odorless.

Carbon dioxide gas, in contrast to other gases properties, the cylinder pressure is not in connection with the residual amount. The cylinder pressure is maintained even when decreasing level, almost to the completely to the depleted level of CO2. The large gas cylinders can be drained to about 1 kg/ (2 lbs) each to complete cylinder filling.

Here, the assumption that the tank pressure of the large gas bottle decreases with decreasing capacity and the cylinder therefore no longer filled to the full capacity.

As long as liquid CO2 is contained in large bottle, the pressure remains constant independent of the level of the bottle and temperature.

The cylinders are completely or almost full and the gas bottle empty with each filling.