Direction of flow in a DIY CO2 reactor. - The Planted Tank Forum
 
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post #1 of 4 (permalink) Old 08-01-2013, 04:33 AM Thread Starter
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Direction of flow in a DIY CO2 reactor.

Hi all.

I am making a C02 reactor to accompany my sump. I have 11 inches of 1.25 inch PVC, with elbows on the end and reducers to my pump tubing. I have a couple of questions, just to make sure I do it 100% right. I attached a schematic.

Firstly, does it matter is the water enters the top of the diffuser (it is vertical, of course) and exists the bottom? Or does the water need to travel up for the system to work properly? I have seen many examples of DIY reactors, but none of them mentions which side is input, and which is output!

Also, my understanding is the CO2 input line should enter at the top of the diffuser, with the line running down to near the bottom. Is that correct?

If I want to add a venturi loop, it should go on the side near the top, and run back into my pump input, correct?

Last, is 11 inches long enough?

For additional info, the pump is running from my sump, through clear tubing, probably at about 400 GPH. I would rather have the input in the bottom because it simplifies my plumbing a bit. The output will run up the tubing.

Thanks for any advice : )
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post #2 of 4 (permalink) Old 08-01-2013, 01:47 PM
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You have the right idea - water enters from the top and co2 from the bottom is fine I've read (Rex did his from the top, as he felt it was better). This way the water is always pushing against the rising co2 giving it more time to dissolve.

I can't comment on the venturi sorry.



In my picture here (~24 inches of PVC) the water enters at the top and the co2 through the blue tube. Water exits the bottom.

if your water entered at the bottom the gas would rise with the water quickly leaving the chamber and not fully mixing. The idea is that the flow of the water fights the natural tendency of the gas to rise - giving you more contact time - more time to dissolve.


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post #3 of 4 (permalink) Old 08-01-2013, 01:50 PM
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I think you could shorten your co2 inlet to be closer to the top - I believe the problem with it so close to the bottom is the gas could get carried away by the current leaving the reactor before it has time to dissolve in the turbulence of the incoming water.

I've not seen a definitive answer on the length of tube - more flow = more length needed. based on my limited research 11inches is probably too short - can you make it any longer?


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post #4 of 4 (permalink) Old 08-01-2013, 03:34 PM Thread Starter
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Quote:
Originally Posted by majorwoo View Post
I think you could shorten your co2 inlet to be closer to the top - I believe the problem with it so close to the bottom is the gas could get carried away by the current leaving the reactor before it has time to dissolve in the turbulence of the incoming water.

I've not seen a definitive answer on the length of tube - more flow = more length needed. based on my limited research 11inches is probably too short - can you make it any longer?
Thanks for the reply. Yes I could make it longer. I have more PVC. The place in the stand I wanted to put it was a bit crowded so I made it a bit shorter, but maybe to much. With the elbow joints, it is probably almost 14 inches though.
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