Leaking cooling water on a chinese compressor

This is the quick connect type ... It is leaking at where the blue plastic collar is....
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This type of quick connector is for tubes with more rigid walls. Inside the connector is a set of mini jaws grabbing onto the outside of the tube after being inserted. I bet the tubes that came with the compressor is too soft to enable a firm grip. I would suggest to replace the connector with the (simpler ) type seen on the Yong Heng. Alternatively you can replace the tubes with this kind : https://www.amazon.com/uxcell-Pneumatic-Compressor-Tubing-Orange/dp/B01N0EYCTS


 
They are QD fittings. They seal with Orings on the out-side of the tube. The tube must be of the exact specified outside diameter. If you have the right tube, the only thing that you can do is make sure that it is pushed in all the way. The tube is held in place by a spring washer type clamp that releases when you press the blue plastic flange towards the brass body. If you can't make them seal, They are available on Aliexpress or perhaps a pneumatic supplier. Or you could replace them with more common spigots.