ANS Brass Check Valve is an excellent check valve that prevents no water flows back to your CO2 Cylinder even under high pressurize CO2 output.

Check Valve prevents water from aquarium to flow back to your CO2 cylinder. It is important to have a check valve because if water enters the cylinder, it can cause rust in the interior of the cylinder and prevent proper CO2 refilling.

Please take note:
Brass check valve is not  design for air pump usage

Related Article : A Complete Guide to Setup a CO2 system