"Iain Miller" wrote in message
...

"Skunky" wrote in message
...

Having recently set up a pressurized CO2 system, I was wondering roughly
how long the bottle should last. It's a 14lb bottle, I'm using around
30-40 bubbles per minute in a 300 litre tank.

Not sure, but ages! Suggest you weigh the bottle now & then again
periodically to track its use. If you don't have a Ph controller on it its
important that you know where it is - when the bottle gets nearly empty it
can "dump" and stick massive amounts of CO2 into your tank & kill
everything...I'd change it when you reckon there is 1-2lbs of CO2 left in
it.

What I keep hearing is that a CO2 dump won't occur if you have a needle
valve installed. Some people have had CO2 dumps with only a diffuser after
the regulator, but I don't think they paid attention to the high pressure
reading when the CO2 ran out, or didn't know that a dump would happen.
Secondly, you don't need to weigh the cylinder to find out when the CO2 is
low. The high-pressure gauge will start to drop when there is no more liquid
CO2.
__
Alex
pcalex (at) hotpop.com