[wkndracer]

Another member posted a Q regarding the end of tank dump and safe guarding the tank via controller/solenoid. As I've never had a cylinder go below 500lbs. prior to refill I was curious enough to post another question to poll others on they're experiences. Thanks to all for responding.

I know other than ambient induced pressure changes that the cylinder won't drift down until all or nearly all the liquid is gone from the tank.

I found this posted some time back.
When a CO2 tank is reasonably full it will contain a mixture
of both CO2 liquid and vapor.

As long as both liquid and vapor are present,
the pressure in the (CO2) tank will depend only on the (ambient) room temperature (not "fullness")
as shown in the table below:

Tank Temperature Cylinder Pressure
(F) (PSIA)
@69° 837
@71° 859
@75° 905
@77° 928
@79° 952
@81° 976
@89° 1080

The gauge pressure (PSIG) is approximately 14.7 psi less than the values in the table above. The temperature to pressure relationship is logarithmic. That’s why it’s not a good idea to leave a full cylinder in your trunk on a hot day.