Repost: Re: Needle valves

[Zxcvbob <zxcvbob at tcw_net>]

This was sent yesterday and I don't think it ever made it into the
digest. My apologies for the duplication if I just missed it somehow. 

Mark and Lisa XYZ <Lisark at arkansas_net> sez:
> I am in the process of building an aquarium and am going "mid-tech" by
> adding a pressurized C02 system.  Unfortunately I lack a needle valve to
> fine tune the amount of C02 that reaches the plants.  I was looking at
> Hoa's site and he said he found one reasonably priced (important issue)
> at NAPA, but I only got a dumb look when I asked about one here in my
> area.
> 
Yeah, I hate that dumb look.

I don't use a needle valve.  I made a flow restrictor that resembles a
"capillary tube" from an automotive air conditioner.  I took a piece of
1/4" OD copper tubing and hammered it flat in the middle until it would
just barely pass any CO2 at 10 PSI.  Then I adjust the flow rate with
the pressure setting on my regulator.  Maybe I get away with it because
I have a two-stage regulator that will maintain a stable 1 or 2 PSI (an
ancient O2 regulator that I swapped the fitting).  But in theory, it
should work at any reasonable pressure.  HTH

Bob

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