I am making a water cooler setup, and I was trying to blow through the water lines (return on the positive cable, and tube going to the torch) and I get zero flow. Does the welder have to be turned on for flow (is there a one-way valve or backflow valve in the torch etc?). I know the passages are small in the torch, but I can force nothing through with everything off.

I haven't used a water cooler yet since I bought my 250EX, I still have the torch that came with the unit.
Thanks for reading.