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Re: Aquatic Plants Digest V3 #821

At 03:48 AM 2/3/99 -0500, James P asked:
>OK, I've checked the web-page, and I can understand the logic, but what is
>this "experimental" regulator that he's talking about? Who makes one, what
>are it's specifications and how much do they cost? 

Great questions.  As for who makes one, the only maker I have found is
Maxitrol, but I am sure there are half a dozen or so in the US.  They are
not expensive either, less than $100, in most cases less than fifty I
suspect.   They take an input pressure of 5 psi or so (12.5 psi emergency
max) and put out a pressure measured in inches of water (1 psi is about 24"
of water).  It is experimental because nobody I know of has done it.

>And why, if this is the
>proper way to set up a "low pressure" system, does EVERY commercial
>manufacturer who sells purpose designed CO2 devices recommend the
>regulator-needle-valve combination?

Because they are trying to push their own appliance.   The only company
that sells a complete system (that I know of) and uses a high-pressure
appliance is ADA.  So his design is fine.   Everyone is trying to use a
needle valve when they really need a second regulator.   They do this
because it is cheaper and simpler.  But it is also unstable unless you use
a very very expensive needle valve (the Hoke, made in England, would be my
choice if I insisted on low pressure via a needle valve).  A Hoke costs
about $100 tho.

To summarize, low pressure systems seem to make more sense until you look
at the details of how you are going to build your system.   But they are
hard to build so they are stable.   If you like a stable system, high
pressure systems are so much easier to build that is worth restricting
yourself to the four or so high pressure appliances available (Dupla, ADA,
Eheim, Point Four).  Of these the Eheim is the clear preference for

Dave Gomberg, San Francisco            mailto:gomberg at wcf_com