I want to thank all of you who responded to my DIY C02 problem that
I was having (i.e. bubbles in a test bucket, none in the tank)
The problem did indeed turn out to be a leak between the bottle
cap and the airline tubing.  I re-caulked again and seem to have
been able to stop the leak.

I am not convinced that the caulk is a good idea for the longterm.
I have seen several diagrams which recommended using a either
a rubber stopper as seen in a chemistry lab for chemical bottles
or a drip irrigation tap.  I have looked for these at local
hardward stores including Home Depot, college campus stores, and
liquor stores that carry homebrew equipment.  I have NOT found
these anywhere, although I found a rubber stopper with a LARGE
hole at a homebrew store.  Can anyone suggest where this item
can be found or a better alternative to the rubber stopper?

Marty Durkin