Dual venturi DIY External CO2 reactor

FacePlanted

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Jul 9, 2007
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Gerry, during the time that your reactor had the gas pocket, how was your venturi loop functioning? You previously said that you never got the gas buildup in your reactor, and that the loop was only circulating water. When the gas did build up, did you get any misting action with the loop? Was gas flowing through the loop? Getting chopped up? Even if you didn't see any mist in the tank, maybe the co2 was getting recirculated from the reactor via V.Loop and was helping efficiency. Maybe this is why you saw pearling much sooner than when there was no bubble in your reactor?

I would think that if your co2 bubbles were totally dissolved before they exited the reactor, that the reduced flow through the reactor wouldn't be able to increase its efficiency any higher (Before air/gas pocket built up in reactor) It would seem that lower flow would increase contact time with the co2 bubbles, but if the bubbles were previously getting dissolved entirely, that lower flow INSIDE the reactor would serve no purpose. Right? I'm just thinking....
I think a weaker pump driving the reactor would make the water flow through the reactor slower, but wouldn't produce a gas pocket inside it. But I think SOME gas buildup is the point of having/using the venturi loop on the reactor. I wouldn't downgrade your reactor pump, but I also wouldn't release the gas buildup either, or only a little bit - but not the entire "pocket". That way you can take advantage of the gas recirculating through your V. Loop.

Sorry for rambling...I tend to write via "stream of consciousness"

Still, I'm curious as to what your venturi loop was actually doing at this time....

Guh-Bye!
-Mike B-
 

Gerryd

Plant Guru Team
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Sep 23, 2007
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Mike,

Venturi loop was pumping gas only at that point in time......I was curious myself and there was no water out of the loop from the reactor, as it is all other times with no buildup.

Not too sure about misting. I do get occasional 'burps' of small bubbles from either of the outflows in the tank, but unsure if these are c02 or not.

I also think that the gas buildup was responsible for the better pearling, but again cannot be certain.

I agree that the gas buildup is the reason for the loop, but with my setup, it does not happen as often/regularly as other setups, not sure why.

There has been no buildup since the other post, so I think that maybe the loop won't do AS MUCH for my setup because of this (lack of gas buildup), but still think it is a good thing.

When I did have buildup, it worked great and as expected, so it is certainly worth keeping......

NP with the stream of consciousness thing.........

P.S. you may have noticed, but I am also verbiose :)
 
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mrkookm

Guest
Gerryd;20630 said:
Mike,

Venturi loop was pumping gas only at that point in time......I was curious myself and there was no water out of the loop from the reactor, as it is all other times with no buildup.

Not too sure about misting. I do get occasional 'burps' of small bubbles from either of the outflows in the tank, but unsure if these are c02 or not.

I also think that the gas buildup was responsible for the better pearling, but again cannot be certain.

I agree that the gas buildup is the reason for the loop, but with my setup, it does not happen as often/regularly as other setups, not sure why.

There has been no buildup since the other post, so I think that maybe the loop won't do AS MUCH for my setup because of this (lack of gas buildup), but still think it is a good thing.

When I did have buildup, it worked great and as expected, so it is certainly worth keeping......

NP with the stream of consciousness thing.........

P.S. you may have noticed, but I am also verbiose :)



My reactor is made from 2" pvc with the reactor mixing chamber being 14~15" tal with an overall heigt of 20". I have the Co2 input & venturi output mounted at the very top of the the reactor with the venturi tube inserted 3/4" pass the top not flush with the top of the 'internal water chamber' so that a little co2 will always remain inside ' your version of the gas bubble but controlled I guess' and the side gas release 3" from the top of the 'internal water chamber' which I do not use.

To help 'suck & mix' co2 form the reactor chamber I have created a basic venturi on the suction line of my external pump which actively sucks the Co2 from the chamber, gets further dissolved by the impeller which then flows back into the chamber of the reactor where some more mixing takes place internally as well as the venturi cycle repeating it self. The end product Co2 enriched misty water gets expelled from the reactor's outflow into my main system pump. In the end this reactor efficiently throws tons of fine misty water into my tank no bubbles at all :D

Now from what you are explaining yours does this very differently from my explanation but I guess at the end of the day getting correct levels of co2 into the taank is whats important and if it works then great.
 

gucci17

Junior Poster
Oct 27, 2007
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Hi guys, this is my first post here. I hope you guys won't mind.

I'm still new to this hobby and I'm having a tough time cramming all this info in such a short amount of time.

I've just set up my pressurized co2 system about 2.5 weeks ago along with dosing EI regime for my 55 gal planted tank. In just that short amount of time the effect it has on my algae infested/dying plants is like night and day.

Anyways, that's besides the point. I'll get back on the topic.

I'm currently diffusing my co2 using the inline pvc reactor based on Rex Grigg's design rigged to the output of my Eheim 2226. I find that it seems to be working well. I've slowly raised my BPS to 1.5 atm because I'm waiting for my DC to come in (which should be anyday now).

What I'm wondering is the advantage of having a dedicated external pump such as a mag/rio/etc. over the Eheim filter. I plan on re-designing my reactor the way Tom has shown in this thread. I can tell just by looking at my spraybar now, that I've lost some water pressure. It probably doesn't help that my reactor stands at around 2ft give or take. I plan on cutting that down to 12" now. These are reasons why I started looking into a dedicated pump for my co2 diffusion.

Now for the design of the dual venturi, the short piece of rigid airline tubing that is used on the top of the reactor to loop back and return the excess co2 gas. Does that not come into contact with water? I was under the impression that the chamber is filled pretty much to the top with water. As I do not have clear pvc so I can't tell. How exactly does that work? Is there pressure in the chamber that pushes excess gas out that rigid tubing and back into the inline of the pump?

I noticed there are many variations to how to loop it back. I read about a post on another forum of a member that drilled a hole into a coupling that was rigged into the inline of the mag pump. Then he epoxied a 1/8" barbed hose fitting into the coupling and attached the looped rigid line to that fitting. Will the water flowing through the inline push back into the looped line? Do you need a check valve on the rigid line? Or is there enough suction coming for the inline to pull the gas through with it? I apologize if this is really vague and hard to understand. Here's the link to his thread -

For all the misting fans out there..... - The Planted Tank Forum

The other question I have is, by having the 12" rigid tubing reaching near the bottom of the chamber which is right by the output of the reactor; does the co2 not get pulled straight out by the flow of water pushing outwards? How does it have enough time to diffuse or rise up into the chamber to get mixed into the water? Am I missing something here?

Oh, one more question. For my 55gal, what is a sufficient external pump you would recommend to get the work done? Something that pushes out 200-300 gph? I'd like to find the best method here before attempting to build another unit.

Sorry for the long post, as I wanted to get in as much as I could in one shot.
Thanks in advance.
 

VaughnH

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Jan 24, 2005
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External reactors use a relatively large diameter tube for the body of the reactor, usually 2" diameter. This means the water is flowing pretty slowly down the tube compared to its velocity in the filter return hose, which has about 1/2" diameter. In fact the water will be flowing at 1/16th of the velocity in the return hose. But, the CO2 bubbles will be rising thru that water much faster due to the buoyancy of the bubbles. So, the bubbles easily make it to the top of the reactor - at least the bubbles in my reactor make it to the top easily. During their trip to the top of the reactor they are exposed to the water and are dissolving into the water. In my reactor I never get a big bubble of CO2 at the top - the bubble never extends down more than about 2 inches into the body of the reactor, because I don't see a bubble in the clear center part, meaning it has to be confined to the opaque part at the top. The bubble contines to be dissolved into the flowing water until it is mostly gone during the time the solenoid is shutting off the CO2 flow. But, during most of that time the lights are out, so I don't need that CO2 to be in the water.

Tom's design will enable me to make use of that bubble by continually removing it and injecting it into the water ahead of the reactor, where it gets another opportunity to be dissolved. Or, as I intend to do it, I will direct that bubble to the powerhead in my tank, so it becomes CO2 mist in the tank. I think this will give me high dissolved CO2 in the water in addition to the CO2 mist. I haven't set this up yet, but I may do it tomorrow.
 
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mrkookm

Guest
gucci17;20711 said:
I noticed there are many variations to how to loop it back. I read about a post on another forum of a member that drilled a hole into a coupling that was rigged into the inline of the mag pump. Then he epoxied a 1/8" barbed hose fitting into the coupling and attached the looped rigid line to that fitting. Will the water flowing through the inline push back into the looped line? Do you need a check valve on the rigid line? Or is there enough suction coming for the inline to pull the gas through with it? I apologize if this is really vague and hard to understand. Here's the link to his thread -

For all the misting fans out there..... - The Planted Tank Forum

No the force of the water will not push the water back if done as shown below. This will creates good suction as long as water is flowing and will not leak either if no airline is on as it is actively sucking in air. The suction is created as water passes the line that is exposed top the water flow and is a very basic venturi. If it is cut flush instead it will push water into the reactor

1z.jpg
 

orangeangel

Junior Poster
Sep 21, 2007
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Sorry to piggy back on the topic.
I plan on getting a pump that does 300 gph through the reactor in addition to the 258 gph from filter.
80 gal tank.
I plan on running the pump with my 1000 reactor and adding the venturi.
Do you run the pump and reactor separate from the filter or inline?
Thanks
Mike Bro.
 

Gerryd

Plant Guru Team
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Sep 23, 2007
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Mikebro,

Inline if possible....

If you can run the outlet of the reactor directly back to the inlet of your main pump/canister, or place it by the intake, then you will distribute c02 enriched water back to the tank via the main return line and mix the c02 a little more in the main pump....

Just don't overwhelm the canister flow with a much bigger reactor flow if that makes sense.....

Or, you can run separate flow back to tank.
 

gucci17

Junior Poster
Oct 27, 2007
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1
Hey mrkookm, thanks for joining the thread.

So are you saying if I drill into the coupling and add the barb, I don't have to 1. expoxy it? 2. leave one end open?

I'm sorry, it takes me awhile to understand how things function w/o having it shown/explained to me in person. I'm kind of a dunce that way.

GerryD > So you're basically saying add a pump of equal or as close as possible to the GPH rating as your canister filter? What effect will that have on the motor in the canister? I believe my Eheim 2226 has a flow of 251 GPH.

Here's a very basic drawing I whipped up on MSPaint to show you guys how my setup currently looks.

setup.jpg


Would anyone mind editing it and posting it so I can get a better idea on how to make this into a dual venturi as Tom explains?
 

milesm

Prolific Poster
Oct 18, 2006
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you would put it between the outflow of your eheim and reactor, as explained above. this is your venturi.


remember, you should drill two holes, insert rigid tubing, one down to the bottom, and one sticking about 2 - 3" into the reactor body; the first one is for co2 input, and the other, for gas recirculation via the venturi.

you have to epoxy the co2 intake tube and venturi tube so that they don't leak (gas or liquid).

hth.
 

gucci17

Junior Poster
Oct 27, 2007
10
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1
milesm > thanks for your response! I'll can easily modify it to do as you've mentioned.

What about the addition of the pump? Is that still necessary? As my flow seems to have drastically dropped with the addition of the reactor and hoses used.
 
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mrkookm

Guest
milesm;20740 said:
you would put it between the outflow of your eheim 'or pump' and reactor, as explained above. this is your venturi.

Correct..... Whether you have an external pump or not this config is always recirculating the Co2, truly mixing it in and dissolving it before the enriched water gets pumped out to the tank.


See the drawing below where I have inserted DIY venturi for optimal performance as well as placement of venturi output as suggested by TBarr. If an external pump was used the basic venturi would be inserted somewhere along the suction line so that impeller would dissolve more co2.

I'm not familiar with a canister filter or its inner workings but some guys on PT.net has suggested to remove the impeller in the canister and use a dedicated external pump to do all the work...... see here

setup.jpg
 

gucci17

Junior Poster
Oct 27, 2007
10
0
1
mrkookm > Thanks for clarifying that for me. Now is there a way I can mess up on the design of the venturi? I say this because I actually work for an irrigation supplier and I have access to many types of fittings. I have an idea in my head atm that I feel would work. I just need to scrummage around work and see if it'll work. I'm just not sure if that would render the venturi design useless. I'll try to take some pics as soon as I get the parts for it. I have nothing against drilling into a coupling and gluing a barbed fitting into it. I just like playing around with things and seeing if they would work.

As for the thread you mentioned. I actually came across it the same night I came across your thread. lol
I'm just afraid of any possible long term effects it may have on my eheim. It's a rather costly device for me to replace should anything wrong happen. ie. burning out the internal components?
I'll resort to adding a pump if I'm not completely satisfied with the flow after a few modifications to the setup.
 

Tom Barr

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Jan 23, 2005
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mrkookm;20744 said:

You can forgo the reactor tube for this arrangement and just use the venturi in line alone.

I'd add a couple of ball valves and loop so that all of the water coming back from the canister is not routed through the venturi, this will allow you to control the flow through the venturi much better and regulate the CO2 mist inside the tank.



Regards,
Tom Barr
 
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mrkookm

Guest
Tom Barr;20760 said:
You can forgo the reactor tube for this arrangement and just use the venturi in line alone.

I'd add a couple of ball valves and loop so that all of the water coming back from the canister is not routed through the venturi, this will allow you to control the flow through the venturi much better and regulate the CO2 mist inside the tank.



Regards,
Tom Barr



Just wanted to clarify that the Venturi shown in the pice is not a Mazzei but instead a DIY version for re-circulating the Co2 form the reactor shown below:


1z.jpg
 
M

mrkookm

Guest
orangeangel;20758 said:
Thanks for the info.

mrkookm, What epoxy are you using for the venturi?
Thanks
Mike Bro

Loctite plastic epoxy that comes in the easy to dispense 'even mix' container. If I was to do it again though would use the original JB Weld epoxy 'steel'.
 

gucci17

Junior Poster
Oct 27, 2007
10
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1
Thanks for joining Tom.

Tom Barr;20760 said:
You can forgo the reactor tube for this arrangement and just use the venturi in line alone.

When you say leave out the reactor tube, how efficient will just having a DIY venturi have on diffusing CO2 as apposed to keeping the reactor?

I'd add a couple of ball valves and loop so that all of the water coming back from the canister is not routed through the venturi, this will allow you to control the flow through the venturi much better and regulate the CO2 mist inside the tank.

Where exactly would I add these ball valves and loop the CO2?

I don't mind having the reactor. I think just by reducing it to 12" as you've mentioned before to someone else and cutting all the hoses to better fit, it will help bring my water flow back up.
 

fjf888

Guru Class Expert
Oct 29, 2007
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I am actually interested in this point as well. With my current reactor, built exactly as laid out here with the venturi tube on the top, I get a lot of mist almost all the time and my plants are growing extremely well. While I like the mist effect I would like better control of it.

Fred
 
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mrkookm

Guest
How tall is your reactor, do you have bioballs, are you using a CAN / ext pump, how far is the reactor out is from the tank out? More details would be helpful for suggestions.