When is there danger of an end-of-tank CO2 dump? - Equipment - Aquatic Plant Central

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Old 07-06-2006, 08:27 PM   #1 (permalink)
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Default When is there danger of an end-of-tank CO2 dump?

I have a 20lb tank with high quality dual regulator and needle valve. My tank was originally at about 900 PSI on the primary regulator, now after many months it's at about 300 PSI on the primary regulator, with a steady output of 60 PSI on the second regulator, which is controlled by a quality needle valve.

At what point is there a danger of end-of-tank dump?

Also, is there still a danger of end-of-tank dump if you use a quality needle valve? Won't the needle valve prevent this?

Is there as much danger of an end-of-tank dump with a smaller CO2 tank? I plan on switching to a 10lb tank when this tank is up, just to save space. With a solenoid it will last as long as my 20lb tank without one.

Thanks for your thoughts, I don't want to take out all of my fish because of a CO2 tank dump!
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Old 07-06-2006, 08:37 PM   #2 (permalink)
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You should change that tank immediately. Once the pressure starts to drop from the regular 800-900 psi it will continue to drop steadily. After the pressure gets too low to be regulated, it will pour forth from your needle valve causing a dump. The needle valve will help a little with the dump, but certainly not prevent it. I change my tank once the pressure starts to drop. I'm not sure what the pressure has to be before a tank dump, but I think it is pretty close to what you have now.
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Old 07-07-2006, 11:28 AM   #3 (permalink)
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I have read that the "end of tank dump" problem was largely experienced back in the dark ages when folks didn't use good needle valves to regulate the flow. So, I doubt it happening to you. But, the dropping pressure means there is no more liquid CO2 in the tank - it is almost empty. Use that as a good advance warning that you must very soon find a time to get it refilled.
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Old 07-07-2006, 12:13 PM   #4 (permalink)
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I'm a newbie!!
What is "end of tank dump"?
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Old 07-07-2006, 02:42 PM   #5 (permalink)
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If you have a decent regulator and needle valve, you will never experience an end of tank dump. I've been using pressurized CO2 for years in many tanks and never witnessed it, even though I often let CO2 tanks run down to zero pressure.

And I don't know anyone else who uses CO2 who has experienced it either. I think it may have been linked to the early days of using pressurized CO2 when the regulators/needle valves available were not quite made for the use we need them for...
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Old 07-07-2006, 03:00 PM   #6 (permalink)
 
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Quote:
Originally Posted by JinxXx0085
I'm a newbie!!
What is "end of tank dump"?
Hehe, end of the tank dump refers to Pressurized CO2 gas suddenly being released into the tank. As already stated, as CO2 in the cylinder becomes low it turns from a liquid into a gas. The gas then can "dump" into the tank when the overall cylinder pressure falls. The excess CO2 dumped into the tank can cause the pH to fall rapidly and kill fish.

Along the same lines of this thread, who has experience CO2 End of the tank dumping?

-John N.
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Old 07-07-2006, 03:16 PM   #7 (permalink)
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Thanks John N. for the explanation! That's definitely something new to me.
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Old 07-07-2006, 03:42 PM   #8 (permalink)
 
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Sure no problem. Though as already noted, this doesn't seem to happen as regularly as in the past possibily due to the better regulators that are offered now. Ah, the hobby is ever changing.

Still we can't rule it out, maybe it does happen still, but I haven't experienced it and haven't heard anyone else recently having this problem. But maybe someone who has had this issue will chime in.

-John N.
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Old 07-07-2006, 04:45 PM   #9 (permalink)
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I haven't ever personally experienced this either. I do let my tanks typically get down to around 100psi before I go fill them back up again. Knock on wood, so far no problems. I tend to agree that perhaps this was a bigger problem in older days.
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Old 07-07-2006, 04:45 PM   #10 (permalink)
 
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It can and still does happen. Not as much though. But you really have to understand how a needle valve works to know that it can still happen. Once the liquid CO2 is gone the high side pressure (on the needle valve) can go up quite a bit higher than it was. This in turn effects the low side pressure and does allow more gas into the tank.


I have actually seen this start to happen on one of my tanks. I was watching and testing and within an hour the CO2 levels in the tank nearly doubled. Now this may or may not cause a problem depending on any number of factors.
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