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Re: CO2 regulation

David Bundy wrote:
> On Sun, 10 Sep 2000 17:25:29 -0700, Wright Huntley <huntley1 at home_com> wrote:
> > The expense of buying multi-stage regulators simply is ridiculous under
> > those conditions. Who needs them? They do nothing particularly useful for
> > most aquarists who have to feed the fish and plants a few times during the
> > month (and can see the gauge).
> >
> > <snip>
> >
> > PS. I think a good needle valve (and higher regulated pressure) in front of
> > the Eheim system could be a useful thing to do.
> Wright, I want make to sure that I understand your comments here.
> Could you (and anyone else who's interested) please comment on which of
> the following 2 setups is better for someone with a sintered glass diffuser?
> (Let's assume the owner travels a lot, is forgetful and that the CO2 setup
> will go unmonitored for long periods of time.)
> Setup #1:  a single stage regulator with a high quality needle valve *OR*
> Setup #2:  a dual stage regulator with no needle valve

Not a terribly good idea, as flow will depend on tank depth and evaporation
of water could increase flow rate. We want to ultimately regulate gas *flow*
rate, not just the pressure.

> Do both setups #1 and #2 perform equally well for day-to-day operation,
> but #2 is just needlessly expensive?

No, as #2 still needs a flow limiter.

> Do both #1 and #2 perform equally well under end-of-tank conditions?


> Does #2 need a needle valve?

Yes. Somewhere along the line, one needs a flow control, and pressure
regulation alone is not the whole answer. A suitably-designed needle valve
could, theoretically, work right off the tank pressure, but very few are
able to withstand 900 psi. A clogged emitter, downstream could cause
spectacular results, too, as the line pressure climbs. The regulator gets
the pressure down to a very level safe for almost any valve and hose. Then
all we need is a restrictor capable of fine adjustment at incredibly tiny
flow rates. [That need usually eliminates cheaper aquarium valves.]

The problem with the Eheim diffuser was that it works so *very* well until
near end of bottle. That has resulted in lots of scrambling to provide
overpressure-relief and all kinds of other arcane "cures." If you want a
uniform amount of gas delivered each day, there is no substitute for a
regulated flow amount.

One unfortunate consequence of the use of a tiny aperture to restrict flow
is the great ease of having it clog and stop flowing. The pressure then
rises to whatever the *pressure* regulator allows. At 20-50 psi that can
cause a hiss when the tubing pops, but won't cause an explosion. I urge that
all avoid the use of teflon tape on any gas fitting that is to be used in
front of a needle valve. Teflon can shred and provide that blockage. Regular
pipe compound or even silicone is much safer. If it is already there when I
get it (as on the rubbish beer regulators I bought ;-) ) I leave it alone
rather than disturb it. I do blow the line out to clear any shreds before
assembly, tho.


Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

"People constantly speak of 'the government' doing this or that, as they
might speak of God doing it. But the government is really nothing but a 
group of men, and usually they are very inferior men." --H. L. Mencken

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