how to tell when your co2 tank is empty?

[Redpappy]

other than weight, is there any way to tell when your tank is about to kick? I pretty much use my tank strictly for carbing up and pushing. Right now my gauge is in the red, so I went ahead and got bought me another tank. i do run 3 to 4 kegs off of my tank(splitter, which is also used to force carb(the set and forget method)) I am asking, more or less because I am noticing my dispensing is slowing down a bit, but my pressure is holding. I"m not sure if I should wait till I see a pressure drop, or not. So far it is still reading 14 psi, even during dispensing.

I believe the tank i have was an old co2 tank, so it does not have weight markings on it. so weighing it( if i had a scale that could) would be useless.

 

[grampamark]

When your tank pressure gauge starts to drop you are running out of liquid C02; what remains is vapor. Depending on the size of your tank you might serve one more keg-you’re basically out at this point.

 

[day_trippr]

There is indeed a precipitous drop as the last of a cylinder is drawn off, but there should be plenty of warning...

Cheers!

 

[Redpappy]

@grampamark would you suggesting till the pressure drops, to get every ounce out of the tank, or just swap it out? I have added a photo of my regulator.

I understand that once the pressure from the tank becomes less than whats in the kegs, they they will try to equalize everything. And I'm not sure if that will create problems with my beer or not ( loosing carbonation)

edit: tank is outside of keezer, temp range is between 62 and 64 at the moment ( basement) does not get any higher than 68.

 

[ITV]

I replaced my CO2 tank today since it was in the red. Once it drops into the red it tends to drop quickly.

It cost me $29 to exchange my 20# tank (Airgas) so I figured that it wasn't necessary to run it completely empty. The last time I exchanged my CO2 tank was 2 years ago (I usually have 4 cornies on tap).

 

[day_trippr]

You're so right. I just picked up a 20# Airgas siphon tank. That $29 for 20# vs $21 for each of my multiple five pounders was too compelling.
I figure the thing will pay for itself in a couple of years

Cheers!

 

[Redpappy]

First tank is a 10# tank, The tank I just bought is a 20#. Minus the purchase of the tank.... its $30 to fill the 10# and $33 to fill the 20#. I thought it was worth the purchase.

I guess I know what i will be doing tomorrow. Thanks for the feed back

 

[Vale71]

Liquid CO2 has a density that is approximately 560 times that of the gas. This means that once you see the needle start to drop you have about 0.2% of the tank's total capacity left or thereabouts. That's not going to last long unless it's a really huge tank.

 

[slurms]

I understand that once the pressure from the tank becomes less than whats in the kegs, they they will try to equalize everything. And I'm not sure if that will create problems with my beer or not ( loosing carbonation)

Looks like you still have a few hundred psi in your tank. Don't think you'd need to even think about that until your needle is pretty much at the bottom.

 

[k-daddy]

You're so right. I just picked up a 20# Airgas siphon tank. That $29 for 20# vs $21 for each of my multiple five pounders was too compelling.
I figure the thing will pay for itself in a couple of years

Cheers!

Was that a special order 20# siphon tank? Can’t seem to locate it on the Airgas website.

 

[Qhrumphf]

Looks like you still have a few hundred psi in your tank. Don't think you'd need to even think about that until your needle is pretty much at the bottom.

As others have said, you shouldn't see much of a pressure drop until the tank is proverbially running on fumes- all liquid CO2 in the tank converted to gas. It doesn't work like a fuel gauge and continuously drop.

The chart @day_trippr posted is awesome. Lines up with what I'd expect a full (or more than almost empty tank) to be at at both room temp and if it's kept in the fridge with kegs. Where the OP's gauge is at (unless its like 0°F and even then looks a little low, or unless it's not reading correctly) it's into that dropping phase and should be replaced or have a replacement in the wings. The fascinating part of that chart to me is the hotter temp and overfill curves. Apparently a hot tank is going to see a more sustained pressure drop. If I'm interpreting that correctly.

I typically don't use bottled CO2 to carb other than slight adjustment, preferring to get most or all of my carbonation via spunding. Since I'm only really using it to push transfers or to push out of keg to pour, I keep an eye on the gauge, and when it starts to drop I make sure I have a replacement at the ready. In the kegerator the drop is slow so I'll wait until it's almost zero and then bang a new can in. Transferring I'll typically swap it out a bit earlier than then kill off that can with the kegerator. Or just replace it.

 

[day_trippr]

Was that a special order 20# siphon tank? Can’t seem to locate it on the Airgas website.

Well, I don't think it was special but I could be wrong. I called in advance and they had two in stock where I picked it up.
The attendant did advise I should do the same (call in advance) when I need to swap it - makes sense because siphon tanks are low volume compared to regular...

Cheers!

 

[RolandD]

You're so right. I just picked up a 20# Airgas siphon tank. That $29 for 20# vs $21 for each of my multiple five pounders was too compelling.
I figure the thing will pay for itself in a couple of years

Cheers!

I'm curious, is there an advantage to using a siphon tank over a regular tank?

 

[Knightshade]

So what if you are getting your tank refilled? Should you release all pressure from the tank prior to chilling and taking it to the shop or?

 

[doug293cz]

I'm curious, is there an advantage to using a siphon tank over a regular tank?

A siphon tank dispenses liquid, rather than gas. In brewing, it would be used to refill smaller tanks. Can't (easily) be used for carbing or serving.

Brew on

 

[doug293cz]

So what if you are getting your tank refilled? Should you release all pressure from the tank prior to chilling and taking it to the shop or?

No, do not release the pressure. If you leave the valve open past the point where CO2 is noticeably escaping from the tank, air will diffuse back into the tank. Any residual O2 in the tank will not be good for the next brewer who gets that tank (unless the filler does a really good purge process prior to refilling.)

Brew on

 

[Qhrumphf]

I'm happy with 2x 20lb tanks rather than a 20lb siphon and 4x 5lb tanks. 20lb tanks are small enough and mobile enough for me. Perhaps a 50lb (or bigger) siphon tank would change that equation. But to each their own.

 

[bracconiere]

i do have a scale, and my 20#'r had 3lb's left in it when it ran out of liquid...which at ~3.5oz's a keg, would have lasted a bit, but i swapped it. better safe then sorry, nothing worse then being half drunk, and running out of co2. having to callin a favor for a ride to the welding shop mid drinking day!

 

[RolandD]

A siphon tank dispenses liquid, rather than gas. In brewing, it would be used to refill smaller tanks. Can't (easily) be used for carbing or serving.

Brew on

I see. Thank you!

 

[day_trippr]

I have three 5 pounders so the siphon tank is now used when one of them gets low

Cheers!

 

[Redpappy]

better safe then sorry, nothing worse then being half drunk, and running out of co2. having to callin a favor for a ride to the welding shop mid drinking day!

That’s the reason I asked.

 

[bracconiere]

That’s the reason I asked.

LOL, and yeah from your pic of the HP gauge, that tanks bone dry...and if you have a leak it's a dead man. $27 man, you need a scale!

 

[jerrylotto]

@grampamark
I understand that once the pressure from the tank becomes less than whats in the kegs, they they will try to equalize everything. And I'm not sure if that will create problems with my beer or not ( loosing carbonation)

For the tank pressure to drop BELOW the keg, you would need to vent it to the atmosphere and then reconnect it to a pressurized keg. Assuming you know better, it ain't gonna happen

 

[Qhrumphf]

That's a concern when attaching a keg (particularly if the liquid is above the gas input) where the keg is already under higher pressure than the CO2 system causing backflow (and there under normal circumstances I wouldn't expect it to get past the regulator). I wouldn't expect an empty tank to do it (unless something happened to create the former scenario, say you have a splitter after your regulator and the other line were opened or attached to an unpressurized vessel or something). In either case a one-way check valve right at the gas post would prevent it. Check valves are part of sanke couplers by default on both gas and liquid sides. A quick googling shows a cornie gas post disconnect with a built in check valve available online (haven't used it). And one could easily be spliced into the CO2 line.

 

[jerrylotto]

That is why I generally vent a keg through the lid pressure relief just before hooking it up. That way, it is always at atmospheric and the lid is always the highest point in the keg. I also try to not fill them that much, but that is another topic for another time.

 

[Qhrumphf]

I mostly use sanke kegs. The one cornie I have I use either as a caustic reservoir when I clean my lines, for nitro cold brew coffee, or for carbonated water. I don't think I've had beer in there in a few years. Basically I don't ever have a dip tube issue depth lol