CO₂ Soda Cylinder Adjustable Adapter Installation & Use Guide

This guide applies to the corresponding TR21×4, CGA320, and compatible Australia / New Zealand Type 30 versions.

Do not identify compatibility by appearance alone. Always check the actual thread type, sealing method, valve design, and product specifications.

Connection Note:
CGA320 and the Type 30 connection commonly used in Australia and New Zealand are not exactly the same standard. Some products may physically screw together because their dimensions are similar, but actual compatibility still depends on thread engagement, sealing design, and cylinder valve construction.

1. Intended Use

This adapter can be used for the following applications:

  • Cylinder Connection
    Connect CO₂ soda cylinders with TR21×4, CGA320, or compatible Australia / New Zealand style connections to regulators, filling equipment, or other CO₂ devices with different thread standards.
  • Cylinder Refilling Connection
    The adapter may also be used as a CO₂ filling connector when the receiving cylinder is designed for refilling and when the gas source, filling equipment, thread connections, and pressure ratings are all suitable.

Available outlet thread options may include:
W21.8-14 / DIN477 / BS341 No.8, CGA320, 5/8-18 UNF, 3/8-24 UNF, G5/8, M10×1, and others.

Please refer to the exact adapter model you purchased for the actual thread specification.

Soda Cylinder Refill Adapter Tr21x4 to W21.8

$34.00 USD

Soda Cylinder Refill Adapter Tr21x4 to W21.8

CGA320 Female to W21.8-14 Male CO₂ Cylinder Adapter Valve

$26.80 USD

CGA320 Female to W21.8-14 Male CO₂ Cylinder Adapter Valve

Tr21*4 Soda Cylinder Adapter for CO₂ Regulator W21.8 / CGA320 Compatible

$26.80 USD

Tr21*4 Soda Cylinder Adapter for CO₂ Regulator W21.8 / CGA320 Compatible

2. Before Installation

Please check the following before use.

① Check the Cylinder Connection

The external thread on the cylinder valve must match the inlet thread of the adapter.

This adapter is intended for cylinders with a compatible thread and a self-sealing center valve / pin-type valve core.

Do not force the adapter onto a cylinder if the thread, valve design, or connection structure is clearly different.

② Check the Outlet Connection

The outlet side of the adapter is normally male threaded.

Make sure the outlet thread matches the regulator, filling hose, or other equipment you plan to connect.

③ Check the Seal

Make sure the sealing ring or washer inside the adapter:

  • Is correctly installed
  • Is not missing
  • Has no cracks
  • Is not badly deformed
  • Has not become hard or brittle
  • Has no visible damage that could affect sealing

Replace the seal before use if any damage is found.

④ Retract the Adjustable Pin

Before installing the adapter, turn the adjustment knob in the reverse direction to fully retract the pin.

Make sure:

The end of the pin sits below the surface of the sealing ring.

This helps prevent the cylinder valve from being opened too early while the adapter is being installed, which could cause high-pressure CO₂ to escape suddenly.

The valve core depth can vary between different cylinder brands. If the pin is fully retracted but still opens the cylinder valve before the adapter is properly sealed, you can replace the sealing ring with a thicker one.

For example, a 3 mm seal may be replaced with a 3.5 mm or 4 mm seal if needed.

This allows the seal to make contact earlier and helps prevent the adjustable pin from opening the valve too soon during installation.

⑤ Check the Adapter Condition

Before use, make sure:

  • The threads are not damaged
  • The adapter body is not bent or deformed
  • There are no cracks
  • The adjustment mechanism moves smoothly
  • There is no serious wear or corrosion

Do not use the adapter if any condition may affect safe operation or sealing.

3. Using the Adapter for CO₂ Supply

  1. Fully retract the adjustable pin and make sure it remains below the sealing ring surface.
  2. Align the adapter carefully with the cylinder valve thread.
  3. Screw the adapter on slowly by hand.
  4. Make sure the thread engages smoothly without cross-threading, binding, or tilting.
  5. Tighten the adapter until you can feel the sealing ring begin to compress and form a proper seal.

Note: Do not use an oversized wrench or excessive force, as this may over-compress or damage the sealing ring.

6. Close the regulator, connected device, and any downstream valves before continuing.

7. Connect the outlet of the adapter to the correct regulator, hose, or other equipment.

8. You may apply soapy water or a suitable leak-detection solution to the connection points to check for leaks.

9. Once the connections are confirmed to be leak-free, slowly turn the adjustment knob to move the pin forward until it gradually opens the cylinder's self-sealing valve.

10. Allow the cylinder to supply CO₂ gradually and monitor the downstream pressure, connections, and equipment operation.

Important:
The adjustable pin is designed to gradually open or close the cylinder's self-sealing valve.
It is not a pressure regulator and does not replace a pressure relief device or other pressure protection equipment.

If the downstream equipment cannot safely handle full cylinder pressure, a properly rated CO₂ pressure regulator must be used.

4. Using the Adapter for CO₂ Refilling

Only refill a cylinder if it is specifically designed for repeated refilling and local regulations allow it.

Refilling Note:
CO₂ is stored as a liquefied gas. The amount filled should be determined primarily by the cylinder's specified allowable fill weight.

A pressure gauge can be used to monitor system pressure, but pressure alone should not be used to determine how much CO₂ is inside the cylinder.
Before Refilling
  1. Confirm that the cylinder is refillable and still within its valid inspection or service period.
  2. Make sure the gas source, filling hose, valves, adapter, and receiving cylinder all have compatible connections.
  3. Confirm that all components are rated for the required working pressure.
  4. Secure the cylinder properly before filling.
  5. Use a suitable electronic scale to monitor the filling weight.
    If the filling system includes a pressure gauge, it may also be used to monitor system pressure and operating condition.
Refilling Steps
  1. Fully retract the adjustable pin.
  2. Connect the adapter to the receiving cylinder.
  3. Connect the filling equipment and filling hose.
  4. Make sure all connections are secure.
  5. Before filling, you may use leak-detection solution to check all connection points.
  6. Open the main CO₂ supply cylinder valve, then slowly turn the adapter adjustment knob so the pin gradually opens the receiving cylinder's self-sealing valve.
  7. Begin filling slowly according to the correct operating procedure for your filling equipment.
  8. During filling, continuously monitor:
    Cylinder weight
    System pressure
    Connection condition
    Any unusual frosting
    Any leaks or unusual sounds
  9. Stop filling immediately once the cylinder reaches its specified allowable CO₂ fill weight.
  10. Fully retract the adjustable pin so the receiving cylinder valve closes again.
  11. Close the main CO₂ supply cylinder valve, then release any remaining pressure in the filling line according to the filling equipment instructions.
  12. Make sure the line is fully depressurized before removing the adapter.
  13. After filling, check again for leaks and confirm that the cylinder valve seals properly.

5. Safety Information

  • Always align the threads carefully and start by tightening the adapter by hand.
  • Stop immediately if the thread feels tight, crooked, jammed, or does not screw on smoothly.
  • Never use excessive force to solve a thread mismatch or gas leak.
  • Never force an incompatible adapter onto a cylinder.
  • Unless specifically required by the product design or manufacturer, do not apply PTFE tape, thread sealant, or grease to the cylinder connection.
  • Make sure the adapter is suitable for the intended gas and pressure rating before use.
  • Do not use the adapter with strongly corrosive gases or gases not listed as compatible.
  • Always operate in a well-ventilated area to prevent CO₂ buildup and oxygen displacement.
  • Never use an open flame to check for leaks.
  • Protect cylinders from impact, open flames, heat sources, and prolonged direct sunlight.
  • Secure the cylinder properly to prevent it from falling over.
  • Stop using the product immediately if you notice continuous leakage, unusual noise, severe frosting, a stuck adjustment pin, damaged threads, or deformation of the adapter body.
  • Do not drill, weld, modify, or alter the internal structure of the adapter.
  • CO₂ cylinder refilling involves high pressure. Always follow local regulations and use suitable equipment and safe operating procedures.
  • Never force the adapter off while the connected line is still under pressure.

6. Additional Compatibility Note

Different CO₂ cylinder brands and production batches may have slightly different:

  • Valve core heights
  • Sealing structures
  • Effective thread lengths

Even if two cylinders have the same nominal thread size, always check the following when using the adapter for the first time:

  • The threads engage smoothly
  • The sealing ring compresses correctly
  • The adjustable pin only opens the cylinder valve after the adapter is properly installed
  • There is no leakage after connection

If you are unsure about compatibility, stop using the adapter and confirm the exact cylinder valve and adapter specifications before continuing.