DIY CO2 question. - The Planted Tank Forum
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post #1 of 8 (permalink) Old 07-09-2007, 02:42 AM Thread Starter
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DIY CO2 question.

I have been running two 2 liter soda bottles for three months now. It seems to work fairly well, I staggered the mixtures so I never have to replace them at the same time. Initially I tried running both bottles into separate bubble counters and then into a 3 way airline connection and into the tank. But I found the difference in pressure would slow one bubble counter right down, almost like the pressure from each bottle was counteracting the other. So I removed the three way connection and put both air lines into one single bubble counter and then from the bubble counter into the tank. I still seem to be having the same issue however. I was wondering how I could eliminate this?

If I can't figure out how to eliminate this issue, I will probably just switch to a single 4 liter juice jug.
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post #2 of 8 (permalink) Old 07-09-2007, 02:53 AM
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Do you have check valves at the bottles? Having two check valves has been the only way I could run two bottles without losing pressure when changing the mix over in one bottle or the other.
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post #3 of 8 (permalink) Old 07-09-2007, 03:08 AM
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I used to use a diy bubble counter but have scrapped it on my DIY co2 tank, not much sense in counting bps if you can't control it. I was mainly using it as a gas separator, to keep yeast funk out of the tank, but I don't have that problem without one either. I suppose it might be the only way to run two bottles into the same line though, since the 'T' method obviously doesn't work well. Why not run two separate diffusers?

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post #4 of 8 (permalink) Old 07-09-2007, 03:26 AM Thread Starter
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Kitbasher I was also thinking about using check valves too, but I wasn't entirely sure it would work. Maybe I will try it.

jaidexl two separate systems would work just fine, but I am trying to work with what I have(Basically I am being lazy and I don't want to build a new bubble counter)

Other than loosing the benefit of always having one solution going at all times, I am seriously thinking about changing to one 4 liter bottle instead. I think it would probably be near the equivalent of what I have going now, if not better and it would be twice as simple. But I think I will try the check valves first.
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post #5 of 8 (permalink) Old 07-11-2007, 06:18 PM
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i'm no expert, but having double the size bottle will probably not last twice as long. I *think* that you'll get many bubbles for the first week or so and it'll die off. Since you already had 2 bottles of 2liters running for stability, going to the 4liter would be a step backwards.

I think your best bet is to get that check valve stated above. That, along with your staggered mixtures of 2 bottles will keep your tank from getting co2 ppm surges.
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post #6 of 8 (permalink) Old 07-12-2007, 01:35 PM
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I had the same issue before and the check valves work perfectly.
I also tried blocking the hoses with a clip before removing the bottle but I still lost pressure.
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post #7 of 8 (permalink) Old 07-12-2007, 02:12 PM
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Instead of a T, have you tried one fo the airline splitters that has the screws in it to stop flow from either side?

They stop flow from an airpump dead. Just reverse it and use the two side for your input, the one side to the tank...

Wondering if they are tight enough to keep the pressure while you change the bottle.

That way you could have both bottles come to the splitter, from splitter to bubble counter, then up to tank...
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post #8 of 8 (permalink) Old 07-12-2007, 02:22 PM
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I tried 2 different airline splitters with screws. A plastic and a metal one. The plastic one leaks like crazy but the metal one leaks just a bit (still too much). When placed in water I could see tiny bubbles coming out of both. I guess that's because they are meant for air and it not that important for airstones and filters....

Still, maybe you have access to better equipment than me.
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