How long will a CO2 bottle last?

[HybridHerp]

I'm looking at a 20lb for myself, which would be shared between a 75 and a 10, so I think we are in the same boat.
One thing I would love to know though, is if people are estimating the time before refill assuming that co2 is going to be on 24/7
I know with myself that I am going to have mine on a timer, that way I'm not wasting any co2 and that way my fish aren't being gassed out.

[Darkblade48]

Originally Posted by Cthulhu

I was under the impression that a 50lb bottle weighted 50lb...?

As mentioned, a 50 pound cylinder holds 50 pounds of CO2 gas; the weight of the cylinder is in addition to this 50 pounds.

In the lab, we use 50 pound gas cylinders; they are impossible to lift up by yourself. If you don't have a dolly, then you'll have a very tough time moving them.

Also, forget about moving them if you have a carpeted floor.

[kevmo911]

Originally Posted by HybridHerp

I'm looking at a 20lb for myself, which would be shared between a 75 and a 10, so I think we are in the same boat.
One thing I would love to know though, is if people are estimating the time before refill assuming that co2 is going to be on 24/7
I know with myself that I am going to have mine on a timer, that way I'm not wasting any co2 and that way my fish aren't being gassed out.

No. Relatively few people have pressurized CO2 without a solenoid, as it makes absolutely no sense to run CO2 24/7. So the estimates you'll see for any given size of cylinder will generally have one agreed-upon timeframe. The estimates lower than that timeframe are usually a mix of 24/7 CO2 and "I've had a small leak for quite awhile but haven't figured it out yet". Estimates over that timeframe are generally people who think they're injecting more CO2 than they really are.

But, again, when most of us talk about a regulator, we're actually talking about a reg, solenoid, and needle/metering valve.

[HybridHerp]

So, overall theme is that a 20lb should work for at least a year.
How exactly can you tell how much co2 is left in the tank? Is it one of the dials on the regulator or something?

[kevmo911]

Well, looking back through the responses, I see 3-4 mo on the low end to 1 year on the high end. I imagine it will be something in the middle. "At least a year" sounds like a stretch, based both on my experience and the responses in this thread, but it'll last awhile.

Your high pressure gauge won't move from around 800 psi for the first 90 or 95% of the life of the cylinder. After that, it will begin steadily dropping. At that point, you'll have a few days to a couple weeks till you're completely out of CO2.

[HybridHerp]

Do you have to wait for the whole thing to drain before getting a refill, or can you get a refill still if there is a little bit left in this thing?

[Steve001]

Originally Posted by HybridHerp

Do you have to wait for the whole thing to drain before getting a refill, or can you get a refill still if there is a little bit left in this thing?

That's up to you.

[AnotherHobby]

Originally Posted by HybridHerp

Do you have to wait for the whole thing to drain before getting a refill, or can you get a refill still if there is a little bit left in this thing?

If you have a dual stage regulator, it doesn't matter if it goes empty. If you have a single stage regulator, there is a possibility of an end of tank dump when the pressure drops, and then you may gas all of your fish.

[jester56]

Originally Posted by HybridHerp

Do you have to wait for the whole thing to drain before getting a refill, or can you get a refill still if there is a little bit left in this thing?

You yourself don't have to wait. But the gas service company will have to dump whatever gas is left in the cylinder to be able to "zero out" the scale and accurately fill the tank... Even the big companies like WESCO and AIRGAS weigh their cylinders. Cylinders all have varying weights. To get an accurate fill volume, they empty the tank, zero the scale, and fill it from that zero point. A 5 lb tank will usually get 4lb 15oz to allow for expansion - especially in the summer. Higher external temperature will increase the pressure in the tank...

[AVN]

Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.

All hail the Dark Lord Cthulhu, long may his reign of darkness be.

[HybridHerp]

Originally Posted by AVN

Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.

All hail the Dark Lord Cthulhu, long may his reign of darkness be.

Someone got hacked

[Cthulhu]

Originally Posted by AVN

Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.

All hail the Dark Lord Cthulhu, long may his reign of darkness be.

[DarkCobra]

Originally Posted by kevmo911

Well, looking back through the responses, I see 3-4 mo on the low end to 1 year on the high end. I imagine it will be something in the middle.

Hehe. I admit I posted a lowball figure, and purposely so. That way, even if the CO2 runs 24/7 into a woefully inefficient diffuser, the OP will never be disappointed; but may be pleasantly surprised.

[Bettatail]

double post

[Bettatail]

accurate estimate on the length of time before refill is impossible to tell, because one bubble a second and two bubble a second makes big difference, time before refill shorten by half.

and a four bubble per second on 20lb is about the time before refill as one bubble per second on a 5lb co2 tank.

there are things that are for sure:
1. put the 20lb outside for safty.
2. make sure there is no leak, some slow leaks that can not be detected by soapy water will shorten the timel; bigger leaks that can be detected by soapy water if left ignore, will dramatically shorten the time before refill.
3. weight your co2 tank so you will know how much co2 left.
4. you can complete list 4, 5,..., if I skip anything,