Does it leak when its conected to the gun? Does it leak with the tank valve closed? Air will come out the hose if its not connected to the gun and you open the tank valve, this is normal even with a regulator. I'm not familiar with Ninjas stuff. Just trying think it though. I have a Airtanksforsale.com Tiger shark 4500 carbon fiber setup. I am looking at a photo of the Ninja set up. The regulator valve likely will not shut off the air flow, if that is what you are trying to do. They are made to set the output pressure you want for the gun then be left at that setting. Use the tank valve to turn on and off the air. Just throwing stuff out to see if it may help. Good luck!