Nemo wrote in message
...
It was a leak at the contact between the line and the cap. Fixed it with
contact cement and bulldog liquid nails. Still suffering from
intermittent
bubble production, though . I get a burst of bubbles through the
airstone
when I shake the bottle, but then it goes ... nothing after a minute or
so.

Thanks for all the replies!

I owe you a quarter.

Incidentally, I don't use an airstone anymore. It's just that much more
pressure for the gas to overcome, that much more likely for the CO2 to find
an unintended escape route. I've heard that the stone can get yucked-up
with goo (terms of art) although I confess I've never seen it.

Watch that seal at the line and cap. I've found that putting repeated
pressure on the connection what with screwing the cap on and off week after
week will often cause the seal to fail eventually.