Is my CO2 tank almost empty? 600psi.....

[user 227424]

This is my first CO2 tank so I'm not familiar with how it runs out, suddenly or gradually. It's been at 800psi since full, about a year now, and just recently dropped to 600psi over the last few uses. I'm wondering if there's just dregs left and I may as well exchange it now? Or if it'll keep going for a while gradually dropping in psi? I'm assuming the pressure only drops at the very end as the last liquid CO2 turns to gas, like propane, thus it's almost empty, but I dunno? I don't want to waste any...

 

[tll77]

the pressure only drops at the very end as the last liquid CO2 turns to gas,

yep, pretty much. I would guess the drop in gauge reading is related to the temperature of the cylinder.

 

[GoeHaarden]

I'm assuming the pressure only drops at the very end as the last liquid CO2 turns to gas, like propane, thus it's almost empty,

Correct.

Where do you store your tank? Temperature can effect the reading. My tank is in the garage and the reading will drop in the winter. Also, had lower but steady readings when I used to store it inside the keezer.

You could always weigh it. The tank should be stamped with empty weight.

 

[day_trippr]

Cgeers!

 

[user 227424]

Not sure how accurate my gauge is but it's been at about 800psi at room temp(65 to 70 degrees) where I keep it, which looks to be what it should be on the above chart. Actually closer to 500psi now. Thinking maybe I'll let it run out to see what's left. According to that chart I may have 10% left which from my 10lb tank is actually a bit. I've been amazed how much this 10lb tank has carbonated!

 

[user 227424]

You could always weigh it. The tank should be stamped with empty weight.

Definitely gonna weigh it when empty.

 

[GoeHaarden]

Definitely gonna weigh it when empty.

I think my 10lb aluminum tank weighs 13lbs empty, but I could be mistaken. I'll check when I can.

 

[dx250]

There may be a tare weight stamped into the neck of tank.

 

[Vale71]

According to that chart I may have 10% left...

No you don't. Liquid CO2 is 500 times denser as gas, once the liquid part runs out what you're left with is just a thimbleful which will run out pretty fast. Time to get a refill! No need to weigh the cylinder now, at 500psi you're left with about 35 times the cylinder volume of gas at ambient pressure.

 

[Dland]

When tank pressure getting too low for beer distribution/carbonation, I take that gas cylinder and use it to feed top of fermentors at low pressure for trub dumps and racking/transfers to lower chance of O2 exposure. Also use it to purge and lightly pressurize cleaned kegs until they are needed next. That way I am not moving tanks around or and use all the gas.

Of course, that requires having more than one tank.

 

[user 227424]

Well since I'm driving to town today where the CO2 exchange place is I decided to exchange it, so I vented off the remaining gas just to see what came out. I'd guess not much more than one keg charge came out, maybe less, so yup good time to exchange. My empty steel 10lb tank weighs 27.5lb, 10lb empty aluminum tank I just received via eBay weighs 14.5lb. Now that I have two I can actually let it run out next time. Thanks all!