I have been struggling to make a pickup tube that works in my keggle. No matter what I do I can't get it to siphon once the water gets below the coupling. I have checked and rechecked everthing for leaks. I have tried teflon tape on the threads and made 2 different types. The first one used a copper tube into a compression fitting and the second was a copper tube soldered into a male thread adapter that screwed into the coupling. Any suggestions?