1 way valves / check valves are necessary on any keg system to provide protection against beer or other liquids contaminating the gas line and regulator.
If beer enters the regulator, it becomes a major job to strip down, clean, sanitise and rebuild the unit to avoid contamination of subsequent batches.
The recommended line for this model 1 way check valve is John Guest LLDPE 3/8" OD
Our John Guest 1 way check valves are provided with the required "C" retainer clips that ensures you have the most efficient and secure seals possible.