Re: CO2 valves for several tanks

> > One other more mundane question that came up has to do with setting up
> > CO2 from one welding tank to more than one aquarium.
> Ahh, an easy question. How to minimize the number of expensive needle
> valves when "ganging" up on a single tank. Simple:
> Tank --- regulator --- needle valve --- gang join --- cheap valves
> The regulator reduces pressure to something the needle valve can
> properly regulate (~50psi) which then throttles it back to about .5
> psi which is easy to balance with the cheap plastic or brass valves
> used for running multiple aquarium bubble toys and aeration stones.
> Steve
	Needle valves don't control pressure, they control flowrate
for a given pressure drop.  If you do it the way suggested above, you
will find that adjusting one of the cheap valves will result in a change
in pressure downstream of the needle valve, and the flow through the other
cheap valves will change.  They will then have to be adjusted themselves.
This goes on!
	It can be done, but getting initial adjustments right will be
a pain in the neck, and any significant change will require resetting other
valves.  The other problem with the cheap valves is that they leak!
Even with a small pressure on their upstream side you are likely to
lose more CO2 than you send to the tanks! 
	Use good valves!

Paul Sears,   Ottawa, Canada.