Attach hose and tank leaks

I have a dual regulator with two kegs attached to one regulator and the other has no keg attached right now. The dial on that regulator reads 0. The problem is that when I attach a hose and without even turning on the gas, the dial shoots up, which would suggest a leak. I put the keg connector in some water and there were some bubbles to confirm this. Previously, I drained a tank of CO2 with this configuration. If I disconnect the hose, things are fine.

I'm not sure where to look for the leak, since the gas is not turned on and the hose doesn't appear to connect in a way that would allow gas to pass through it.

Any suggestions for how to address this? Thanks in advance.

Tim in MN

Huh, your question is rather confusing.
This is what I am assuming your situation is, correct me if I am wrong:
You have a dual regulator, the first regulator is set at some PSI and the hose from it goes to 2 kegs (via some sort of splitter) and you have no problems with that regulator.
Your second regulator has the knob/screw turned all the way out so it is set at 0 PSI, and the hose attached to this one is not going to a keg at the moment. Now this is the confusing part, are you saying that if you the connect the quick disconnect (QD) at the end of this hose to a keg that is carbed/carbing that the dial then jumps to some PSI value? This is normal as it is showing that there is now pressure on the low pressure side of the regulator (i.e the hose is pressurised from the pressure in the keg).
Where were the bubbles coming from when you put the QD in water? This is were the leak is that caused you to drain a whole tank of CO2.
If you reg is set at 0 PSI no additional CO2 should be floowing through the regulator and the leak should only let all the pressure currently in that keg out only. Fix that leak then you will be able to turn the regulator up and start using it.

Let me know if I have confused you even more and I'll try again