CO2 Ran Out and No Dump... (luck?)

[125gJoe]

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Guess I got real lucky.. Got back from a vacation week and had zero CO2 left in my 10 pound tank! I have been watching the readings, but I guess not close enough...

I'm surprised I didn't lose the fish from a "CO2 dump" I've heard about.

Been using the tank for appox. 10 months...

:o

[nvision]

good to hear.

i think it depends on how open your needle valve is. if small enough, it can still regulate up to a lower pressure. but if you normally run 3-5 b/s, it might be wide enough to trigger a release...

[Matak]

I don't use pressurized, so I'm in the dark on this one. How can a gas system "dump" under reduced pressure? It doesn't make sense to me.

[famman]

He's referring to the 'pH dump' as the c02 is lost from the water. (I think).

[djlen]

No, I believe he's talking about what happens to SOME pressurized systems when the gas in the tank is used up. Some tanks do what is known as "dump", which means they empty the balance or most of the balance of their gas into the tank, all at once. This can, and probably will kill all or most of the fish in the tank. Your CO2 tank contains liquid and vaporous gas. As the vapor is used the pressure in the tank is reduced. The liquid burns off and turns to vapor, increasing the pressure again. This all happens at a relatively steady rate so you don't see the fluctuations on your gauge. There comes a point at which the liquid gets used up and your tank pressure will drop as the balance of the vapor is getting used up. This is where some regulators have difficulty holding the pressure and 'dump'. Some people believe that the needle valve will stop this from happening, but if you have a certain pressure going to it and the pressure increases, so will the amount of gas going through it.
EDIT:
I want to give credit for most of the information in the above paragraph to "Off Ice", a moderator on the Fish Geeks forum.
I quoted it, basically because it is the clearest, and easiest to understand explanation on the subject I've ever heard.
Just passing it on.....

This can be avoided by simply watching your gauges especially your tank pressure gauge and when it gets below 800psi, get it refilled. At that point there is probably in the area of 2% of the gas left in it and, from my standpoint it's worth it to get it refilled at that point than risk the consequences of a tank dump.
Moral of the story......watch your gauge closely and when it starts to drop watch it even more closely, especially when it's getting below the 800psi level.
Len

[Jason B]

There are a number of variables that would determine if a C02 dump would effect your fish. I would imagine it depends on the size of aquarium, tightness of lid, size of C02 tank, time of day and quality of reactor to name a few.

I have a 5lb on a 90 gallon and when it dumps the fish are not effected. That doesn't mean I like it to happen. Just that it has happened without consequences. Fish can take a fair pH swing when everything else is going well. It would take a fair amount of C02 to raise levels to kill fish in a bigger tank.

Also having a needle valve doesn't stop it. And the key is watching the gauge. When it starts to drop you are a few days from a dump. My gauge reads full at 550psi if I remember right.

[Matak]

Thanks. You learn so much here.

[famman]

thanks djlen!

[Skittyfish]

It seems that I have read several horror stories of dumps and dead fish. I noticed on Sunday that my tank had reached the part that says to refill the tank...I was terrified! Took it off Monday evening, worried about water siphoning out all night, and had it refilled on Tuesday!

I am too afraid not to keep and eye on mine.

Though my worst fear is for the pressure to release all at once, what is that called? gassing off?

[bobalston]

Please see this posting on anyther board for good explanation of co2 tank dump:

http://www.fishgeeks.com/modules.php?op=modload&name=phpBB2&file=viewtopic&p=71249&highlight=co2+tank+liquid+vapor#71249

Bob ;)

[125gJoe]

Originally posted by djlen
.... ...Some tanks do what is known as "dump", which means they empty the balance or most of the balance of their gas into the tank, all at once. This can, and probably will kill all or most of the fish in the tank.

......watch your gauge closely and when it starts to drop watch it even more closely, especially when it's getting below the 800psi level.
Len http://gordon.sourcecod.com/images/flagicons/american_flag.gif
Guess there was no "dump"...
The shop where I get CO2 refills said the best way to know how much is left is to weigh the tank now and then... It's very hard for me to get to the tank to weigh it, but I'm working on that.

I have a "10LB." tank.
CO2 refill is 10 pounds -- the empty tank weighs 14 pounds.
So, 24lbs. total weight is a full tank.

Thanks for the replies! I need more room under my aquarium!

[125gJoe]

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bobalston, thanks for the link!