On Sun, 30 Aug 2009 15:41:09 -0700 (PDT), ransley
wrote:

On Aug 30, 12:53*pm, ben wrote:
One of the toilets in the house has an intermittent issue with air
bubbles.

Occasionally, when just sitting there unused, a single bubble of air
will 'blurp' as it reaches the water surface in the bowl. *It might
happen once or twice in a day, or as many as ten times (possibly
more). *The toilet has zero problems as far as function go.

I think we first noticed this last year but it went away after a
while. *It returned a couple months ago.

I've read that a clogged waste vent could cause this. *I've looked in
them (from the roof) an don't see any blockage. *The other toilets in
the house don't have this problem either.

ideas?

Can you really see down the vent, maybe run water and a garden hose
down it.

My thoughts exactly. Tree frogs hang out in the deep shadows of the
pipe :-/