Emptied CO2 cylinder

[wkndracer]

Have you ever drained a CO2 cylinder to zero psi?

[Regloh]

I haven't, but i would imagine there is still plenty of CO2 left, when the gauge says its close to empty

[cah925]

You can but it's not recommended. There is usually a "dump" of gas at the end that the regulator can't/doesn't stop. The effect is much more gas in the tank than desired which has the potential to kill fish. pH probes attached to the solenoid usually catch the drastic pH fluctuation and cut the gas off before serious damage is done.

[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.

[kid creole]

I take it to 0 just about every time.

[Wasserpest]

I usually refill my tank when it shows between 300 and 500 psi. At that point, there is probably a week or two of CO2 left, which isn't a big deal if I miss out on it.

[jjp2]

I have run a CO2 to 0. I didn't get an end of tank dump, but did get dibris in the needle valve which took me a while to get out of it. I reccommend changing when it gets under 500.

[Regloh]

Originally Posted by jjp2

I have run a CO2 to 0. I didn't get an end of tank dump, but did get dibris in the needle valve which took me a while to get out of it. I reccommend changing when it gets under 500.

Do you think the two events are actually related? I'm trying to think how the fact that the tank is empty would cause debris to come out... or where ever it came from.

I think the number one reason to not let the tank run completely empty is that you can get it refilled on your terms, not when the damn tank decides to go empty. Unless you always have a backup tank, then it doesn't matter.

[houstonhobby]

I did it several times with my JBJ, never noticed a problem.

[Left C]

I've ran mine empty with pH controllers and I have ran them empty with dual stage regulators. No problems for me.

[jjp2]

Originally Posted by Regloh

Do you think the two events are actually related? I'm trying to think how the fact that the tank is empty would cause debris to come out... or where ever it came from.

Not sure. I've let others run dry before and that was the first time I had an issue. I have to swap tanks due to where I get the refills so could have been something in the tank.

[Hoppy]

I want to refill my CO2 tank before the gage hits zero, but I rarely catch it at that time. It generally goes to zero before I notice it. The only disadvantage that I know of is the one Regloh mentioned. Usually my zero pressure occurs on Friday evening, often when Monday is a holiday. I know there is a thermodynamic law that dictates that, but I forget its name.

[Regloh]

Originally Posted by Hoppy

I want to refill my CO2 tank before the gage hits zero, but I rarely catch it at that time. It generally goes to zero before I notice it. The only disadvantage that I know of is the one Regloh mentioned. Usually my zero pressure occurs on Friday evening, often when Monday is a holiday. I know there is a thermodynamic law that dictates that, but I forget its name.

Hoppy, I believe the name of the law is "Murphys Law"

[Hoppy]

Originally Posted by Regloh

Hoppy, I believe the name of the law is "Murphys Law"

Yes!! Now I remember.