External CO2 Reactor-Slightly New Design

[VaughnH]

(This article cross posted on APC forum.)
This is the external reactor I just finished making this weekend. It features a built-in bubble counter at the bottom, to eliminate the problem of keeping water in the bubble counter, and it reduces the number of CO2 leakage points. It has a bleed valve at the top to bleed off any trapped air bubble. The center section and the bubble counter are made of clear PVC, and some of the fittings are brass, but the rest is just hardware store standard PVC fittings. Here are some detail photos:

 

[VaughnH]

Additional detail photos of this reactor:

 

[Professor Myers]

Well Done Hoppy ! I like your DIY projects. Seems Like if you want a truly functional external reactor the OTC's always come up short. For what they cost retail you have quite a bit of headroom for materials. Very Cool... What is the flow rate through the reactor ? Prof M

 

[VaughnH]

Right now the flow rate is zero! It isn't hooked up yet. But, I hope to get it installed today, using a Rena Filstar XP3, which gives 350 gph (or, they say it does). I have a lot of questions about how well it will work, such as, can I see the CO2 bubbles in that tube at the bottom, will the bubbles be huge, will the bubbles get swept out the outlet, will the bubbles float to the top too fast and collect uselessly there, and, always the biggest question - will it leak? Stay tuned!!

 

[Professor Myers]

Right now the flow rate is zero! It isn't hooked up yet. But, I hope to get it installed today, using a Rena Filstar XP3, which gives 350 gph (or, they say it does). I have a lot of questions about how well it will work, such as, can I see the CO2 bubbles in that tube at the bottom, will the bubbles be huge, will the bubbles get swept out the outlet, will the bubbles float to the top too fast and collect uselessly there, and, always the biggest question - will it leak? Stay tuned!!

So long as you introduce media like Bio-balls etc... to aggitate and perpetuate gasseous exchange the Co2 will not collect uselessly ! The problem most folks have is too little flow through the reactor so Co2 levels are often unstable causing frequent punctuated swings in Dissolved Co2 instead of a more linear stable supply. Most all of the retail designs sold are kinda half baked !!!

 

[VaughnH]

My built-in bubble counter isn't a good idea! (It hurts to say that!) Because the open end of the 1/2" tube is where the bubbles escape into the main body of the reactor, the bubbles tend to be almost 1/2" in diameter. I suspected this would be the case, since the bubbles are not formed at the tiny diameter of the CO2 inlet hose barb, but further up the counter, where the diameter is much larger. I couldn't think of a good way around that or I would have made it differently. It is possible that tilting the reactor so the bubbles go faster from the barb into the counter body would iimprove things. I may try that tomorrow. So far I haven't had time to see how effectively this mixes CO2 into the water in the reactor - the big bubbles go pretty quickly to the top of the reactor, but it should be pretty turbulent up there.

 

[Tom Barr]

V-

The Tube, the 2"Clear PCV should act as a bubble counter if you add the CO2 in at that point. I think having a straight in/out is easier than 90 degrees.
Also, use 1/2" in/out grey barbed PVC adaptors, they provide good flow through.

You can also add a irrigation drip valve to bleed off the excess false gas.

Drill directly into the bottom of the clear PVC for the
CO2 inlet and glue a CO2 line into the unit there. The out lwet can go down a bit and still count the bubbles coming up also.

Some folks add a disc or a fine airstone there, no bubble counting then, but more a hybrid mist/reactor method.

Note, you can make a loop with the false gas bleed and feed this back into the pump intake. This will remove any false gas and improve the dissolution of CO2, it's somewhat like my old idea of a venturi loop, just modifed for an external seal reactor.

You may also add a venturi at the end of the CO2 flow line right before the tank and drill a CO2 bleed line about 1-2" down on the reactor's side.

I've been meaning to show folks a simple external CO2 reactor DIY project for no less than 2 years now, I'm finally done with most of the year's school work and am research only now.

Finally time to play bass, ride, travel and do some fun projects.

Regards,
Tom Barr


Regards,
Tom Barr

 

[VaughnH]

There is a limited amount of room under my tank in the cabinet, so the 90 degree bends allow one to make the reactor longer without having to allow for the gradual bend of a hose above and below it. That's why I chose to use tees as I did. I have been surprised at how easy it is to see the CO2 bubbles in the clear 2" PVC section - if I had known that I wouldn't have bothered with the 1/2" PVC bubble counter. Now I am thinking about your idea of a venturi in the filter return line right next to the tank, with the gas bleed line going to that - an out of tank CO2 mist system. That would be an easy thing to add.

 

[VaughnH]

The reactor works fine! Within an hour or so I had 30 ppm of CO2, the same as I had with the Barr internal venturi reactor with the same flow rate, but with much more water current in the tank. All of the plants were pearling within a couple of hours and for the rest of the lights on period. With the CO2 off, the ppm of CO2 drops pretty quickly - the drop checker is actually solid blue in the morning vs. being blue green with the venturi reactor. I'm still thinking about adding the venturi in the line just ahead of the spray bar, and I don't see it being a difficult thing to do. Just putting a double ended barb fitting there, with the CO2 ported to the center of it would work, but probably not as well as if the ID were smoothly necked down a bit more. Unfortunately my hardware store has 1/2" and 3/4' barbs, but no 5/8" ones, and the hose is 5/8" I.D.

 

[VaughnH]

I learned something today. I finally got around to cleaning and pruning my tank. Please don't ask how long it has been. First I forgot that you have to unplug the hoses from a Rena Filstar XP3 filter before you do maintenance, so I lost the prime on the filter. Then the fun began. I filled the inlet hose, plugged in the hoses, and lost the syphon quickly. This happened over and over for almost 2 hours, before I noticed that when I unplug the hoses I get a loud hiss like a vacuum escaping, but there can't be a vacuum in the hoses, since they are under water at the top. Finally I looked at the External CO2 Reactor. It had a bubble of CO2 at the top, trapped. So, I tried opening the bleed valve at the top as the filter tried to fill with water to prime it, a blast of pressure escaped, and water soon followed, as the filter, at long last primed itself.

I can't remember reading anywhere that this would happen. But, now I know. When priming that filter an external reactor needs to be bled at the same time or the incoming water can't get past the slightly pressurized CO2 bubble in the top of the reactor. That was a hard lesson to learn.

 

[Professor Myers]

Well...? Yes actually 4 or 5 times at least. I believe it's human nature to overlook our own foilble's. Even more so as we get older...In fact I'm counting on it ! That's my story and I'm stickin to it !!! Prof M

 

[nopq475]

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