Refilling Adapter Kit for W21.8 to CO2 Tank How It Works: 1. Chill the soda siphon cylinder in the freezer for 1 hour. 2. Attach the CGA320/W21.8 fitting to a commercial CO2 gas cylinder. 3. Remove the cap from the black adapter, then securely tighten the black adapter onto the CO2 cylinder. Ensure the knob on top of the black adapter is fully turned upward (in the highest position). Do not turn the knob downward — this would depress the 6 mm valve pin and close the valve, preventing CO2 flow. 4. For large CO2 cylinders: invert or lay the cylinder horizontally. Note that some large cylinders do not include a dip tube (siphon tube). 5. Slowly open the valve on the large CO2 cylinder. Opening too quickly or too far may trigger the safety valve and stop gas flow. Listen for steady airflow to confirm proper operation. 6. After approximately 15–20 seconds, the cylinder is fully filled. 7. Close the valve on the large CO2 cylinder. 8. Open the bleed screw to release any residual gas. 9. Unscrew the adapter from the CO2 cylinder. Important Notes: 1. If liquid CO2 remains in the cylinder, invert the CO2 tank during refilling — some tanks lack an internal dip tube. 2. The cylinder must be empty before refilling. Pre-chilled cartridges fill more completely. 3. Open the large cylinder’s valve very slowly when filling to avoid triggering the safety valve (6 mm pin). 4. This adapter is not compatible with RPV (Residual Pressure Valve) systems. Check your tank before ordering. If your tank has an RPV valve, select the “RPV Pushing Adapter” option. Some RPV valves can be removed using a hex wrench — verify compatibility first.