Repair help

[Jonatas]

Hi, how are you? I hope you're doing well.

The side tube isn't working properly because it isn't building pressure when I screw it in. I'd like to know the name of this connector so I can buy a replacement.

[Fred Davison]

That is called a male Luer connector.  The one in you photo is this type:   https://www.mcmaster.com/51525K121/

but that is not a side tube, it is a mouthpiece tubing connector. 

Luer fittings are a standard type of connector used worldwide.