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Regulators
Scott,
It is always hard for me to resist replying to some of the CO2 posts.
We clearly agree that the NO-1 is really not suitable for most aquarium use.
However it really isn't "cheap". It is actually a nice, inexpensive,
needle valve designed and manufactured for industrial control applications
that use MUCH higher flow rates than our one or two bubbles per second. I
would think the niche for a metering valve that could reliably regulate flow
in the cubic-feet-per-week range would be very small (just us plant nuts)
and would therefore cost a lot more than we would want to pay. There was a
very extensive post a year or so ago where someone (Dave Gomberg?) wrote on
flow rates and degree of control. My recollection was that one of the Nupro
models was the only commercially available valve that even came close to
having an adequate range of control at the very low flow rates we use. The
reason I keep bringing this up is because I have not found a suitable
replacement that I can recommend. There are plenty of valves available but
they either cost too much or are not "better" enough than the one I am using
to justify a switch. I plan on trying a out a couple in the future and I'm
always open for suggestions. In fact I have a manifold system driving three
tanks that would make a good comparison test set-up if I can ever get
motivated.
I also agree that the high pressure systems probably do not require a
metering valve if certain precautions are taken.. My personal experience
with high pressure systems though is limited to one trial with an Eheim
diffuser and I did not like it. I had trouble maintaining steady flow rate
because the diffuser would become clogged over a few days and required
constant cleaning. I much prefer a low pressure type set up and inject the
CO2 directly into the intake of a canister filter. Besides, My
understanding of the "end of tank dump" problem leads me to believe it is
more likely to be a problem on a single stage system without a metering
valve.
In all probability there are only a very few of us that like to tinker with
this enough to build our own. There are more commercial systems offerings
every year and the prices are coming down. If I were only doing one or two
tanks and didn't already have a couple of extra regulators and spare parts I
would probably just buy a complete set up. But.. If you want a two stage
system with independent solenoid and needle valve control for 3 tanks for
under $300, then you gotta roll your own.
Lyndle