Hi Dustin,
A lot of this reiterates what Chuck states...
You're actually talking about 2 different things here. What happens in
a tank dump is that the regulator tries to equalize the pressure on
both sides of itself, thereby continuously adding co2 to the aquarium
at a rate faster than it can be used. The easiest way to avoid this is
to use a needle valve between the regulator and tank. I got the one
from Dave Gomberg (wcf.com) and I'm very pleased with it. Now with a
tank dump here's what happens. Co2 is added to the tank so fast that
most of it escapes to the atmosphere. With a tight fitting aquarium
cover the co2 will blanket the waters surface, and prohibit an oxygen
exchange. This is what kills the fish. There is no oxygen available at
the waters surface since it's all co2. I don't know for certain if
this phenomena will happen with a tank that doesn't have a cover on
it. The easiest way to avoid a tank dump is to use a needle valve and
watch the regulator pressure on the tank side (high gauge) of the
regulator. As long as there is co2 liquid in the pressurized tank your
pressure will remain constant at somewhere near 800 psi. When all of
the liquid is depleted the pressure will start to drop on the high
side of the regulator. It's going to take some time for it to get from
800 psi or so to 200-500 psi, where you're getting near the "failure"
point of the regulator. I've also read that if this "tank dump"
happens damage to the regulator is likely. IME with the "dose rate"
I'm using it takes about 2 weeks for the tank to get to 500 psi. At
that point I disconnect the regulator and the tank and I take a short
ride to the welding shop. The only way to get liquid from the
pressurized tank to your aquarium is if the pressurized tank has
liquid in it and it falls over. The way I prohibit this is to tie it
to the center brace in the tank stand.
I think the reference you're speaking of with liquid getting into the
aquarium has to do with the sugar/yeast method of generating carbon
dioxide. I'm completely green on that subject, and I'll leave that to
someone that knows what they're talking about.
On Thu, 2 Jan 2003 17:31:51 -0800, "Dustin"
wrote:
Alright,
By a tank dump then, you are talking about alot of co2 *gas form* comming
out all at once and sufficating the fish?
I thought you meant liquid comming through and contaminating the water. I
called the welding shop, where I bought the co2 tank, and they said the
liquid could only come out if there was a tub inside the tank, which is
normally only used for large tanks *50gal+* or Paint Ball Tanks.
Which needle valve do you prefer, or is there such a thing?
Thanks!
Dustin
"Chuck Gadd" wrote in message
.. .
On Thu, 2 Jan 2003 02:58:26 -0800, "Dustin"
wrote:
THanks for the input Cannibul, that I did buy that system. Wish I hadnt
know, maybe I can get a refund.... I dont like the idea of loosing all
the
fish...... was it because he didnt have a needle valve, or because the
product is junk?
The product is perfectly fine. The problem is that the system doesn't
use a needle valve.
But even without a needle valve, the system is SAFE, and works fine.
The issue is what is known as an "end of tank dump". Co2 regulators
are intended to operate with a tank pressure of 800-2000 psi (CO2
pressure will never get that high, it's usually around 800-1000psi).
On the regulator, the high pressure gauge is marked in red from
0-600psi. This is because, when the CO2 runs out, the tank pressure
drops down. The regulator is unable to properly regulate when the
tank pressure is very low. In theory, anything below 600psi is a
problem. In practice, I've run my regulator (from Dave Gomberg) down
to 300-400psi with no "dump". But in any case, once the pressure
drops below the regulators minimum, the regulator looses the ability
to regulate the output properly, and the output pressure will rise.
Since with the "high pressure system" the pressure directly controls
the bubble rate, this rising output pressure results in a CO2
overdose.
At the extreme end, the regulator can completely loose control when
the tank pressure drops very far. At that point, it would vent all
the remaining CO2 in a sudden burst.
For all of these cases, simply adding a needle valve will provide a
safety net.
But, if you keep an eye on the tank pressure, it's easy to notice
BEFORE the tank pressure drops very far. Unlike watching your car's
gas gauge, the CO2 pressure will remain constant (around 800-1000psi
depending on the temp) until the tank is 99% empty. When the CO2 tank
is filled, the CO2 is under pressure, and is in a liquid form. As
long as ANY liquid CO2 remains in the tank, the pressure stays at that
800-1000psi. Once all the liquid is gone, the pressure will start to
drop.
On my tank, with a fairly high CO2 flow rate, I would get about a week
from the time the pressure first started to drop, till it reached the
600psi mark. So even without a needle-valve, if you glance at the
CO2 pressure once every few days, you will see it in time to prevent a
problem.
On my system, with a needle-valve, I intentionally let the pressure
drop all the way down. I run the regulator pressure at about 6psi
normally, and then control the bubble rate with the needle-valve. I
usually have a bubble rate around 2-3 bubble per second. As the tank
pressure dropped below 300psi, the output pressure rose up slowly to
about 15-20psi. I never saw a true "end of tank dump" with a big
spike in output pressure. And the bubble rate (because of the needle
valve) didn't increase much, less than 1 extra bubble per second.
Possibly a bigger issue with the Dave Gomberg high pressure system, if
it's the same as when I bought mine several years ago, is that the
tiny little Eheim diffusor isn't very effective in large tanks. In my
75g, I was unable to get acceptable CO2 levels using it. I ditched
the eheim diffusor, added a needle-valve, and built my DIY reactor,
and I've been very happy ever since.
Chuck Gadd
http://www.csd.net/~cgadd/aqua