I just had my 20# CO2 cylinder filled up two weeks ago and the damn thing is
empty again!

I used the plastic washer (1) AND Teflon tape to be on the safe side. I put
the regulator on REAL tight, dumped the whole thing in the bathtub and
filled the tub with water to just above the fill pipe. I opened the valve
all the way and rolled the tank around a bit, being careful to keep the
gauges and solenoid out of the water. No sign of leaks.

So WTF is going on? Leaky solenoid, leaky gauge, sudden depressurization,
VERY leaky hose? Any help appreciated.