I have printed these from petg and pctg, and both seem to work fine.
Additionally, you also need a roughly 16mm x 2,5mm (5/8" x 0,1") O-ring.
PS. If you are using a hose clamp to secure the connection, be careful not to overtighten the clamp, it might break the union. These are plastic after all ;)
The author marked this model as their own original creation.