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Sudden CO2 discharge

Many of you may recall my report of excessive CO2 discharge from a cylinder
leading to the loss of almost an entire tank of fish.  I believe I now
understand how this occurred.

When CO2 is bled from my tank into a regulator whose high pressure side has
a straight-thru connection to the cylinder and whose low side leads
directly to the reactor (without benefit of a needle valve, with the
regulator set to one pound), when the pressure in the tank drops from its
initial value of around 800psi to around 400psi, the regulator suddenly
fails to regulate and passes the gas straight thru from the 400psi side to
the output side.   Needless to say, this dumps about 25 cylinder volumes of
CO2 into the aquarium.  This is sufficient to saturate the water with CO2
and to displace all O2 from the space between the water surface and the
cover glass.  And the sequel is that the fish die.

I do not know if this form of failure is a unique bug in my regulator or is
common to all regulators of a particular type, but I will ask my CO2 guy
and see what he says.

The following recommendations may reduce the chance of your suffering a
similar tragedy:

1.  Use some serious regulation after the regulator, like a needle valve.

2.  Keep the regulator output at a fairly high pressure, like 15psi gauge,
so that a failure is less serious.

3.  Don't try to use the last of a tank.  When the pressure drops to 700psi
very little gas is left anyway.   Don't try to economize.

4.  Consider shutting off the cylinder cutoff valve if you are going to be
away for a while.

5.  Consider installing some kind of pH alarm.

6.  Look at your tank.  Learn to recognize normal behavior.   My wife
noticed she couldn't see any fish for 12 hours before I realized what had
happened.   She did not mention this to me.  It could have saved some fish.

Hope this helps you enjoy your plants more.    Dave

Dave Gomberg	mailto:gomberg at wcf_com
FormMaestro  <http://www.wcf.com>