Thoughts on this PVC Reactor Design - The Planted Tank Forum
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post #1 of 10 (permalink) Old 06-26-2016, 06:42 AM Thread Starter
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Lightbulb Thoughts on this PVC Reactor Design

Toying with the idea of building this reactor out of 3" pipe. Flow rate will be around 350 gph and a steady stream of big co2 bubbles.

What Im trying to decide atm is the best place to have CO2 going in, at point 1 or point 2.





Any thoughts on which point would be best, or any other aspect of the design?


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post #2 of 10 (permalink) Old 06-26-2016, 06:57 AM Thread Starter
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Option #3 -

Here's one I made out of 2" pipe. Still have the top half including the T with the CO2 fitting.



Thought about just adding a section of 3" below the T for increased dwell time. But what Im afraid of is a bubble collecting up top where much of the co2 never makes it into the 3" part.

This is also my dilemma as far as where to have it going in in the above design.


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post #3 of 10 (permalink) Old 06-26-2016, 11:19 AM
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Point 1, pull the 1/4" co2 tubing through a 7/32" hole.



I tapped a small hole at the top of mine and connected a 2nd CO2 tube to it to prevent gas pockects at the top of the reactor, the other end faces the intake of my sump pump.

Connecting the CO2 through the T causes the CO2 bubbles to crawl up the side of the reactor doesn't it?


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post #4 of 10 (permalink) Old 06-26-2016, 01:05 PM
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A couple of things I like about the above design;
1. The incoming water is moving at a fairly high speed when it dumps into the reactor chamber. This will cause a lot of turbulence fight at the top of the reactor which will help breakup the bubble of cO2 should it form.
2. Having the cO2 line positioned this way should help - but remember, the high current of water coming in is going to blast the bubbles everywhere.
3. Burr, if you inject the cO2 in at point 2 (which is basically the way mine is setup), the cO2 will flow right with the water into the top of the reactor. The incoming water will create turbulence and the bubble will float at the top until they are dissolved.
4. With a clear housing like mine and like the one above, you soon realize the bubbles don't really go down more than 6-8". A 20" tall reactor may not be needed.
5. Last thought, on the reactor above, I can also see bubbles getting trapped at the top of the lower T, just before exiting the chamber. This design idea would further limit small bubbles from getting into the tank.
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post #5 of 10 (permalink) Old 06-26-2016, 02:00 PM
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This is a question that comes up often as we tend to not want to use things that work but often want to improve them---even when it doesn't work.
Singalong has a pretty good design that is close to the original which was proven to work well enough that it became a common standard for reactors!
But then folks do add things like changing the way the CO2 enters. Rather than trust what works we often see complaints about a bubble of gas. Pulling the tubing in through a hole so that it meets the water flow mid-stream works and doesn't leak.
I find the idea of increasing pressure in the reactor is a bit questionable if it is open at the end? Overthinking/engineering is a common trait when dealing with new stuff. I just go with the item the way they work and the original design works very well.
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post #6 of 10 (permalink) Old 06-26-2016, 06:22 PM Thread Starter
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Thanks for the input guys, very helpful

Quote:
Originally Posted by PlantedRich View Post
This is a question that comes up often as we tend to not want to use things that work but often want to improve them---even when it doesn't work.
Singalong has a pretty good design that is close to the original which was proven to work well enough that it became a common standard for reactors!
But then folks do add things like changing the way the CO2 enters. Rather than trust what works we often see complaints about a bubble of gas. Pulling the tubing in through a hole so that it meets the water flow mid-stream works and doesn't leak.
I find the idea of increasing pressure in the reactor is a bit questionable if it is open at the end? Overthinking/engineering is a common trait when dealing with new stuff. I just go with the item the way they work and the original design works very well.
Thanks. I understand the concept of co2 entering the center of the waster column, and why it is better. I just cant get comfortable with the idea of using the undersized hole method. It may not leak in 100 years....doing it that way just doesnt appeal to me.

Quote:
I find the idea of increasing pressure in the reactor is a bit questionable if it is open at the end?
How is it questionable? Anything that restricts flow going out will increase the pressure behind it. A 90 degree barb instead of a straight one, a smaller exit hole, a cut off valve that you can partially close, increase the flow going in, etc

Pressure dissolves co2 better than anything. Think soda pops. They arent made by swirling bubbles round and round and round. They are made using pressure.

Ive built a few different versions recently, similar to the 2" I posted above. Some worked fairly well. Some collected a bubble up top that you could begin to hear after a few hours. Some blew mist out the bottom.

Adding a cut off valve to increase the pressure helped every single time. So did bio balls. Whether the bio balls helped by agitating the water/holding micro bubbles, or because having them inside created more resistance which increased the pressure...cannot say for sure, combination of both maybe, but they definitely helped as well.

Here is a youtube vid where the guy fixes the bubble in his cerges by increasing pressure.

https://www.youtube.com/watch?v=Itj-qxlKmIo

The only reason Im not using the 2" pictured above...is not because a bubble built up. There was no bubble. It is because I had to restrict the flow too much with the cut off in order to get 100% dissolution. I want the ability to have more flow coming out.

Quote:
Originally Posted by Immortal1 View Post
A couple of things I like about the above design;
1. The incoming water is moving at a fairly high speed when it dumps into the reactor chamber. This will cause a lot of turbulence fight at the top of the reactor which will help breakup the bubble of cO2 should it form.
2. Having the cO2 line positioned this way should help - but remember, the high current of water coming in is going to blast the bubbles everywhere.
3. Burr, if you inject the cO2 in at point 2 (which is basically the way mine is setup), the cO2 will flow right with the water into the top of the reactor. The incoming water will create turbulence and the bubble will float at the top until they are dissolved.
4. With a clear housing like mine and like the one above, you soon realize the bubbles don't really go down more than 6-8". A 20" tall reactor may not be needed.
5. Last thought, on the reactor above, I can also see bubbles getting trapped at the top of the lower T, just before exiting the chamber. This design idea would further limit small bubbles from getting into the tank.
Im going to use "point 2" in the diagram as you suggested, was leaning that way to begin with. May cut the 3" pipe down to 16'" or so. Length is not an issue because I have plenty of vertical space. As far as I know being longer than necessary doesnt hurt anything?


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Last edited by burr740; 06-26-2016 at 07:54 PM. Reason: .
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post #7 of 10 (permalink) Old 06-26-2016, 07:22 PM
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Reason for my doubt on the pressure question is due to the amount of added pressure. how much can one add with that small change? I would not expect it to be more than 1-2 PSI at most and that would not seem to change the figures enough to matter. The pressure can only reach the limit that the pump will add and with mag drive filters, that isn't much pressure.
But the design and figuring out what to do is always a large part of any DIY if we are not following what somebody else has done. My reason for following the Grigg's design is that I don't want to try to reinvent the wheel since the Grigg's design works so well.
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post #8 of 10 (permalink) Old 06-26-2016, 07:54 PM
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Another option is to put another small tube in, to use the venturi effect to remove any excess bubble that forms. You can run it from the reducer elbow to a point further up by point 2. It will suck any built up gas from there to the other end and continually cycle it until it adsorbs, removing the bubble.


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post #9 of 10 (permalink) Old 06-26-2016, 08:05 PM
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If the cylinder is sized properly it won't matter where the bubbles enter the stream, be it in the water line or halfway down the reactor or near the bottom. The cylinder should be large enough that the downward flow of water is NOT enough to push the bubbles out the bottom. They will all end up at the top of the reactor until they are absorbed into the stream.
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post #10 of 10 (permalink) Old 06-27-2016, 04:01 AM Thread Starter
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Quote:
Originally Posted by PlantedRich View Post
Reason for my doubt on the pressure question is due to the amount of added pressure. how much can one add with that small change? I would not expect it to be more than 1-2 PSI at most and that would not seem to change the figures enough to matter.

But the design and figuring out what to do is always a large part of any DIY if we are not following what somebody else has done. My reason for following the Grigg's design is that I don't want to try to reinvent the wheel since the Grigg's design works so well.
Even a slight increase in the pressure inside will make a big difference in what comes out, or how it performs in general. I can say this with confidence after having tried a few different designs recently. When one had a problem I'd chop it in half, add something, change something, try it again, etc.

I respect that you use the exact Griggs design because it works well for you. But Im trying to go a slightly different route here, even if it means a lot of trial and error.


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