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Re: Aquatic Plants Digest V3 #17

On Sat, 10 Jan 1998, KHOO Guan Chen wrote:

> Steve Turner wrote:-
> > I have a DIY CO2 setup which I have running for about a year. Twice
> > in the past week I have encountered a strange problem. For some
> > reason the liquid (yeast/water/alcohol) is being sucked out of the 
> > 2l pop bottle into the tank and the pop bottle has collapsed somewhat.
> You have filled your pop bottle nearly to the top?
> This had happened to me before. MY guess is that the yeast had stopped
> fermenting and the CO2 remaining in the bottle dissolved into the tank
> water resulting in a large  drop in pressure in the bottle.

Now there's an interesting idea!  

Honestly though, I think the drop in pressure due to diffusion of CO2 into
the water would be balanced by diffusion of O2 and N2 back into the
bottle.  And we're talking about something that would probably take a long
time to happen. 

Others have responded with the idea that the suction was caused by placing
the CO2 outlet into the intake of a pump, which then became clogged to
produce very low pressures, or into the venturi which is designed to
create suction.  Either of these could cause the problem, but a partially
blocked intake would probably produce a lot more suction than a venturi. 

I can think of two ways that will at least help avoid the problem.

1) Don't use two liter pop bottles.  Their sides are flimsy and tend to
collapse with very little suction.  Try using fruit juice or sport drink
bottles that are made with heavier plastic and have fluted sides.  They
are a lot stronger. 

2) Don't put your CO2 outlet directly into a pump inlet.  Position it 
below the pump inlet so that the rising bubbles get caught in the stream 
and pulled in.  That way if the pump inlet does get partially blocked the 
high suction won't pull stuff out of your CO2 bottle.   

Roger Miller

In Albuquerque, where I spotted a bald eagle by the river on my way to work!