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Tony Rubin's CO2 quest

Tony is putting together a pressurized CO2 system:......

James Purchase responded:

"A comment on the regulator Tony. Most good regulators have two dials,
one which measures the pressure inside of the compressed gas canister,
another one which measures the pressure of the CO2 as it leaves the
regulator. This is usually called a single stage regulator, and is what
practically everybody uses. 

The number of gauges on a regulator have absolutely nothing to do with
the number of stages.  A lot of the cheaper hobby set-ups have none at
all because a useable gauge can cost almost as much as the regulator.
Most good CO2 regulators are two stage.  Regulating the very high CO2
tank pressure to 15 psi even at low flow rates can cause single stage
regulators to freeze and malfunction.  "Practically everybody" that has
a CO2 system has a two-stage regulator because of the physics.

The pressure of the CO2 within the cylinder is going to stay pretty
constant until just before the gas is all gone, so the first dial won't
change much. The pressure of the exiting gas will vary as the CO2 level
inside of the cylinder decreases, that's why you want the second meter -
you might need to make adjustments over time.

As you noted, a CO2 gauge on the pressure side will remain relatively
constant until the tank is nearly empty.  However the low pressure gauge
will stay at the set pressure until the very end provided system flow
rates remain within limits.  Even on a cheap two-stage regulator, a few
hundred psi should be sufficient to maintain steady output pressure.

There are two stage regulators available - but they are usually a lot
more expensive. They will keep the pressure on the output side
practically constant regardless of the dropping level of CO2 within the
main cylinder.  For a single aquarium set-up, it's probably overkill to
use a two stage regulator."

The cost of hobby systems are very high because of many factors
including limited market, packaging, liability, and profit concerns.
Saving money and getting a superior system is a good motivation for
building your own.  There is enough discussion on that topic in the

I don't think it is overkill to have a reliable system whether it is a
single tank or a multi-tank set up.  A few years ago my Sandpoint system
failed in the full open position and killed a tank full of very valuable
animals.  That is why I have made an effort to understand how these
things work.

Lyndle Schenck