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Discussion Starter · #1 ·
I just built a DIY CO2 reactor pictured below which is in-line of an Eheim Ecco 2236. It seems to work OK. As time goes on the reactor starts to gurgle more and more. Right now after 24 hours of operation it sounds like a babbling brook. This is at about 2 bps. CO2 is dissolving since my plants are pearling like crazy.

The noise is not my concern but rather that the trapped CO2 may airlock my canister. Right now if I power off the canister, wait 20 seconds and turn it back on I can hear the canister churning through the CO2 before running normally. I assume that as time goes on it will eventually reach the point where the entire reactor is nothing but a CO2 air bubble. Bleeding the trapped CO2 is easy enough, I just pop off the output quick connect and let the nozzle back siphon and force it out but I dont want to make this a daily chore.

Is this normal for this type of reactor or is there a design flaw in my reactor? It is 2" pipe, down to 1" for the CO2 injection port and then on to the heater. Do I not have enough flow since the reactor, heater and UV are all in-line of my 2236?

Pic:
 

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Looking at the size of the lines that attach to the reactor, I'd say 2" is too big. I had the same issue when I hard plumbed my filter, I had 1 1/2 inch lines, and could never get rid of the eventual bubbles that would appear until I downsized to 1 1/4 inch line.
 

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Discussion Starter · #3 ·
Looking at the size of the lines that attach to the reactor, I'd say 2" is too big. I had the same issue when I hard plumbed my filter, I had 1 1/2 inch lines, and could never get rid of the eventual bubbles that would appear until I downsized to 1 1/4 inch line.
Hmm maybe I will build another reactor using 1.5" pipe and see if there is a difference. Another option is to break out an unused 2213 I have and use that to run the UV loop since I suspect that is where, besides the media in the canister, the most flow loss is.

I am experimenting at the moment by seeing how long it takes for the gurgling to disappear on its own after I shut the CO2 off. So far after about an hour it is much quieter than before suggesting its rapidly dissolving the trapped CO2. I am going to set the bps to around 1 bps tomorrow and will see if that achieves enough CO2 saturation without gurgling.

But I must say this reactor is immensely effective. I used to have to dump in 10+ bps through my powerhead diffuser just to get it to my desired pH. Now 2 bps gives me the same levels. :proud:
 

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Maybe you can tilt it some and the gas will evacuate.

Also, you can add a bleed valve similar to the one on the AM 1000 reactors. Then plumb it so that it evacuates into the air or the aquarium.

There are either some pictures of a PVC reactor with a bleed valve or either a DIY of one somewhere. I just searched and I couldn't find it. I found comments by a few people suggesting adding an air bleed valve though. Here's one.
http://www.plantedtank.net/forums/diy/79150-my-new-diy-co2-reactor.html#post750698
 

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Is the CO2 input at the bottom?

As far as flow, those barb fittings really add to head loss. Not much you can do other than oversize them where possible.

SteveU
 

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Discussion Starter · #6 ·
Is the CO2 input at the bottom?

As far as flow, those barb fittings really add to head loss. Not much you can do other than oversize them where possible.

SteveU
The CO2 is injected at the bottom.

And why are the barb fittings a source of head loss? I would have assumed the most head loss comes from the elbows but I am no plumbing expert.
 

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I'd definitely take the elbows out if you build another reactor. That 180 deg turn to your heater is probably cutting down your flow quite a bit. A modest curve w/ just your tubing, that doesn't crimp, will help. The T for your airline is also causing some drag. I had the best results when I built a reactor w/ no Ts, no elbows, just straight through w/ larger barbs on the ends, hung up w/ zip ties & hooks to the side of my stand. Going down to 1 1/2" will help your flow and might not affect your dissolution. Every canister model/gph will have a different ideal reactor length and width. Play around. I should also mention, I've never found a combo that didn't build up SOME gas later in the lighting period, but always gone by the a.m.
 

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We have to use them but many barb fittings have a considerably smaller ID and that can account for substantial head or friction loss. It's the same with any fitting where the water will "crash" into that surface.

Generally speaking slip fittings have an advantage in that they have less friction loss. For instance a 3/4" regular 90° slip is 1.2 ft friction loss and the threaded version is 4.4 ft. The I.D. must be smaller to allow room for the threads and still keep the O.D.

I know some of the barb fittings offered up at Home Depot and Lowes have very restrictive ID's. I try and use the "Dura" plastic line as they seem to have put some thought into their design.

SteveU
 

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Discussion Starter · #9 ·
Thanks for the help. I removed the heater and UV and put them on another loop so now it is just the reactor in-line of the 2236. But that did not work as the reactor just air-locked the canister.

I bled the reactor, tilted it about 15 degs off vertical and will see if that improves the bubble issue. If that fails to correct it I will scrap the reactor and implement the suggestions you made in making a new one. I should also mention that the CO2 never switches off, even at night, since the reactor is only 'just' able to keep up with CO2 outgassing at the surface or plant consumption. My pH monitor never reads below 6.7 despite my desire for it to be at 6.4 so the CO2 is never switched off. The reactor is simply not dissolving the CO2 fast enough.
 

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I thought the CO2 was best injected at the top so it's close to the input and has time to dissolve. Input flow should push the CO2 towards the bottom. Sounds like the flow rate isn't enough to keep the bubbles from floating up.

SteveU
 

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interesting thread. Makes me think about revisiting my reactor efforts. I had a 2 inch x 18 inch PVC reactor with 2x2" 90 degree elbows, one at the input and one at the output. It was attached to a Rena XP2. At night I would hear the gurgling and when I had to restart the XP2 after cleaning, it could be quite difficult. Maybe I should try again with 1.5 Inch PCV. Have any suggestions on length? I am using an inline diffuser at the moment. Works very well if, you like the looks of 7 UP.
 

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Discussion Starter · #12 ·
I thought the CO2 was best injected at the top so it's close to the input and has time to dissolve. Input flow should push the CO2 towards the bottom. Sounds like the flow rate isn't enough to keep the bubbles from floating up.

SteveU
Yeah I believe that is my problem. My only last fix at this point is to take out the filter floss in the canister and see if that ramps up the flow. In all likelihood I will rebuild the reactor with 1.5" pipe, slip fittings, and a bleed valve at the top. Maybe I'll order some clear PVC so I can see what is going on in the reactor too.
 

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I'm not an expert at this, but I fabricated the "Rex Gregg" CO2 reactor, utilizing 2" PVC. I followed his instructions to the letter. My CO2 input is closer to the top of the reactor. I have gurgling noises closer to the end of it's time cycle. By positioning the reactor at a tilted angle (perhaps 40 degrees), much of "backed-up CO2" is eliminated. I operate this with my Eheim Classic 2217, and I works great!:D
 
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