My bubble rate takes some time to become stable. The key is to make small
adjustments and check after a long settling time.
Like you I am using a cheap needle valve from a local hardware store.
When this valve is completely closed I can get about 45 bubbles per minute
if I adjust the pressure to ~4 pounds. If I crack the valve just a fraction
of turn the bubble rate goes way up. So for me it is best to leave it
'closed' and adjust my rate by pressure. I will make 1/2 to 1/4 turn at the
presure regulator and check after a hour or so. After a few tweeks over a
couple of days every thing remains stable. Leaving the needle valve alone
and adusting presure may go againt convetion wisdom, but it works for me.

Scott


"Matt Hanson" wrote in message
...
I've had a very bad problem over the last few days with my brand new
high pressure CO2 setup. (not DIY!)

I cannot keep a constant bubble going for more than a few days at a
time. Here are the factors that I have eliminated:

1) not too long of a length of tubing, to or from anything. Shorter
tubing would eliminate any kind of pressure hold. Additionally, I ran a
very short length of the larger diameter line, for this very reason.

2) constant temperatrue - not sure if even a change of 20 degrees would
have much effect, but nonetheless, it's not a problem.

3) no leaks - I bubble tested with soapy water.

4) not a regulator or valve disturbance - very sure.


So then, I have checked these things, and found nothing to be out of the
ordinary. Yet, one day I have 1.5 bubbles per second, the next day,
about 1 bubble every 10 seconds.

Does anybody else have this kind of experience?

BTW - for what it's worth, I have one of those "needle valves" from Home
Depot. I'm already starting to suspect the problem might be somewhere
there. It's not even really a needle valve, so the control is less than
desireable. I'm not quite sure how they can even be marketed as a
needle valve. Tell me folks, is it in the valve?