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Endless needle valve saga

What is the big deal with this endless gibberish about needle valves? Get 
yourself a dual gauge, single stage regulator, put a needle valve on it (with 
or without a solenoid), set your bubble rate and unless your needle valve 
decides to open wider by itself you will not have to worry about the rate 
going any higher. A given opening on a needle valve will flow a bit more gas 
when the CO2 tank is full and tank pressure is greatest, and that rate 
(bubble count) will only lessen as the tank pressure/step down pressure 
drops. This is my experience for three years with four CO2 tank/regulator 
setups. I have never had an increase in the amount of gas/bubble count 
passing thru the needle valve as the tank pressure lessened.

Imagine your household water pressure is 80 psi and you have 1/2" ID copper 
tubing everywhere except at one point where it reduces to 1/4" ID. You have 
effectively reduced the operating diameter of all the tubing before it to 
1/4" ID also, and the water will go thru 1/4" ID tubing only so fast at 80 
psi. Reduce the household pressure to 60 psi and you will not see an increase 
in the flow rate, only a decrease.

How could you possibly have an increase in the flow rate of CO2 thru a needle 
valve of fixed size opening with less pressure pushing the gas thru the 
opening? A full CO2 tank with 900 psi would flow more thru a needle valve 
than the same tank with 600psi many months later. 

I have only had to slightly increase the opening of the needle valves in my 
setups as the tank pressure drops. I have never had to decrease the opening.

Buy a single stage, dual gauge regulator, which has step down pressure 
adjustment and don't worry about it.

Oh, by the way, can anyone tell me what the color of water is in a bucket!

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