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RE: CO2 (yet again!)

Just when I think I'm beginning to understand something, I find out I know
squat. <grin>

I needen't go over my reasons for wanting an equal input of CO2 into each of
the 4 tanks I wish to set up (I can hear your cheers from here).

But I see several well respected people, advocating different methodologies,
and I don't know enough except to be dangerous (to myself and my fish), so
I'm requesting clarification from all sources.

Dave Gomberg wrote:

> Good plan, but if you use Eheim reactors (diffusors) you can ditch the
> bubble counters and the check valves  and the needle valve.  That was what
> I was trying to say earlier.  All you need is the 4 t valves and 4 Eheims.
> The t valves let you balance any slight production variations in
> the Eheims.

So, Dave, you are saying that I just need:

Regulator - T-Valve Manifold with 4 output points, each attached to an Eheim
diffusor. No Needle Valves. I assume you would also include a check valve to
protect the regulator from backflow?

From my understanding of regulators, the most commonly used are "single
stage" models and I have just spent a while reviewing the material on the
BOC Gases website. They carry numerous models of both "single stage" and
"dual stage" regulators which are suitable for use with CO2.

"The BHS 500 brass single stage regulators are recommended for very high
purity, inert gas applications where slight variance in delivery pressure is
acceptable as cylinder pressure decreases."
"The BHT 500 brass two stage regulators are recommended for high purity, non
corrosive gas applications where constant delivery pressure is required as
cylinder pressures decrease."

Now, both of these regulators will deliver output at 15 psi, which from what
I _think_ Dave is saying is what is required for the operation of a sintered
glass diffusor.

Is THIS the reason you suggest that I ommit a Needle Valve(s) in my setup?
would the addition of Needle Valve(s) render the sintered glass diffusors
ineffective? I thought that Needle valves modulated flow, not pressure? How
would I modulate the flow of CO2 through each diffusor to ensure equality of
CO2 injection into each tank in the absence of a needle valve, especially in
light of Erik's comments?

Do "T valves" have an adjustment mechanism? (sorry, but I have never seen
one, so I don't know) If they _are_ adjustable, how precise is the
adjustment and how well would it hold it's adjustment over time and with
varying input pressure (single stage regulator)?

I have seen many posts in the archives where comments are made about
"fiddley valves and regulators". I'm not interested in "fiddley" - that is
why I proposed the use of the Nupro valve over the ARO - it is supposed to
be much more substantial and precise and capable of holding it's adjustment
over time. Similarly, to my mind the use of a two stage regulator (while
more expensive to purchase) would provide a constant output pressure
independant of the cylinder pressure, meaning that I would have to "fiddle"
less over time as the CO2 in the tank got released. Is this right, or am I
wishing in the wind again?

I don't mind making adjustments, but if I am buying adjustable equipment, I
want equipment which will hold it's setting - I am NOT a fiddler. That's why
I use Eheim equipment -
quality costs but in the end to me it's worth it. I'm not interested in
wasting money, but quite often I think that looking too hard to shave a few
pennies just ends up wasting more money in the end when the "bargin" proves
ineffective and has to be replaced.

How does this setup jive with what Erik has said:

> I do not beleive there is *any* way to insure equal delivery of CO2 to
> each tank by a means other than adjusting valves or relying on similarity
> of manufacturing.  I'll say it all over this post.

Comments, Dave?

> The line to each tank must have its flow independently reduced in order to
> overcome the differences in backpressure of the water in each tank.

A curve ball from left field, if ever I've seen one (and I thought baseball
season was over <grin>).

Erik continues:

> If you are using a traditional reactor (I like the term "counter-current"
> that was used here today), each line must have a valve to accomplish this.

It sounded sensible to me when you first mentioned it, and I liked the setup
which you showed me, but I misunderstood what Dr. Dave told me about his
prior experience. I knew he was speaking about an air system, not one using
compressed gas, but I failed to recognize that there are substantial
differences (I said that I knew just enough to be dangerous).

Would this also follow for a "sintered glass diffusor"?

> If you are using a sintered glass diffuser, my understanding (from Dave's
> posts) is that the diffuser acts as the resistive element, producing the
> equivalent flow of a bubble per second at 15 PSI... I don't have one, so
> those of you in the know, please correct me here!

Dave, please jump in here.

> I think Steve posted a third possibility today with the daily manual
> measured injection into inverted jars (aka the old "Tetra Bells" method).

Let's not even _go_ there.... As I said, I'm _not_ interested in fiddling.

> > Dr. Dave suggested that I set up the system as a closed "loop",
> wherein an
> > equal pressure of CO2 is provided to each tank. He described a

> If you have separate resistive elements (needle valve &/or diffuser) for
> each tank, the height will not contribute effectively to the system,
> because there is no way for the backpressure to push upstream of the
> needle valve or diffuser.
> But now, reading ahead...you are proposing
> Cylinder -> Regulator -> Needle Valve -> Ring of T Valves each going to a
>                                          reactor
> Oh my, this is the same trap I fell into when I first tried this...I was
> too cheap to shell out $40 a pop for multiple Nupro valves...

I'm _not_ looking for the CHEAP way of doing this. I'm looking for the
CORRECT way of doing it. Many people here have much more experience dealing
with pressurized systems than I do - my experience with pressure cylinders
is limited to being a regular user of "Edge" shaving jell <grin>.

I'm not expecting anyone to actually design this thing for me - I can be
pretty inventive when I understand something, but it seems that there might
be various opinions on how this might be accomplished.

Tell me Erik - with YOUR setup (using multiple NO-1's) - do you think that
they would power sintered glass diffusers and provide me with sufficient
adjustment capability to be relatively certain that each tank was receiving
the same amount of CO2? Would the use of a "dual stage" regulator instead of
the more common "single stage" regulator help with the ability of the system
to maintain equality over time?


James Purchase
Toronto, Ontario