Scott Rogahn wrote:

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,

It doesn't sound like your needle valve is much of a valve!