"Colin" wrote in
:

As long as you've not got a screw-on lid, then surely any pressure
build up will just pop the cork?

I use a standard 5L glass demijohn with a pre-drilled rubber bung. The
airline is siliconed into the bung. I'm certain that if anything does
ever clog, either the bung or airline will let go before the glass.

Ahhhh OK... Yeah a bung would do the job nicely. I was thinking this was a
screw-on lid...

The best idea I've heard for a pressure relief device though is to fit
a T-connector in your airline, close to the bottle, with a piece of
balloon over the end. You'll soon see a blockage 'cos the balloon
expands, and it would pop if the pressure got too high. I'm sure there
was a discussion on this or one of the other aquaria groups just a few
weeks ago.

That is a good idea

~Empty
--
"I'm constantly forgetting my own phone number. Quite simply,
it's because I never call myself. (I used to, but I was never
home. I just gave up after a while. I figure if I want to talk
to me, I'll just have to do it in person.)" -Walker