Thoughts About In-Line Reactors

[banderbe]

First, the details:

2" diameter, 24" long "Rex" style reactor, powered by a Filstar XP2. Nothing else inline.

Last night I was playing around with my pressurized CO2, and I found that if I turned the bubble rate way up (just for a short time of course) that rather than seeing bubbles come shooting out of my spraybar, I heard the water at the top of my reactor begin to trickle, the way it does for the first day after installation or after cleaning the filter when there's an air pocket at the top. So I realized that my flow rate is so slow that CO2 is able to rise to the top of the reactor. It still gets disolved, but it stands to reason that this effect creates a limit as to what the reactor can accomplish in terms of disolving CO2 into the water. Above a certain bubble count, CO2 is just gathering at the top of the reactor and disolving into the water at a fixed rate. This also seems to make sense because I cannot seem to get my pH below 6.8, and no matter what I never ever get bubbles out of the spray bar.

I wonder if this is the way the reactor is supposed to function. I had been under the impression that the ideal reactor would hold CO2 in the water column as it dissolved- that the flow down was roughly equal to the rate at which CO2 bubbles rise up. I also wondered about people who have had pH crashes due to problems with pH controllers connected to their regulators. From what I can see, my reactor would not crash my pH but would instead just build up a large pocket of CO2 at the top.

I am seriously considering ditching my reactor all together and going with a venturi design.

[Rex Grigg]

Never had that problem. And I have them being powered by both a XP2 and a XP3.

[rey]

FWIW I've been thinking about replacing my Tom Barr style venturi reactor with an in line, but have held back because I didn't want to lose any flow rate off my canister, and I always liked the convenience of linking the reactor to the lights for no CO2 overnight. I never liked having the venturi inside the tank, but Tom's thread elsewhere here (search "rio venturi" to find it) suggests a way to eliminate the in-tank reactor tube by using Rio's new RVT powerheads. My only complaint against ANY venturi style reactor is the tank water looks like club soda...

[banderbe]

Originally Posted by rey

FWIW I've been thinking about replacing my Tom Barr style venturi reactor with an in line, but have held back because I didn't want to lose any flow rate off my canister, and I always liked the convenience of linking the reactor to the lights for no CO2 overnight. I never liked having the venturi inside the tank, but Tom's thread elsewhere here (search "rio venturi" to find it) suggests a way to eliminate the in-tank reactor tube by using Rio's new RVT powerheads. My only complaint against ANY venturi style reactor is the tank water looks like club soda...

The pearling from my plants makes it look that way anyway

[banderbe]

Originally Posted by Rex Grigg

Never had that problem. And I have them being powered by both a XP2 and a XP3.

Rex, correct me if I am wrong but you do not use 2" diameter PVC in your designs, right?

[Rex Grigg]

1.5" or 2".

[Naja002]

I may not be understanding what You are getting at, but let me offer this:

heard the water at the top of my reactor begin to trickle, the way it does for the first day after installation or after cleaning the filter when there's an air pocket at the top.

I think what these Reactors need is a simple "Venturi" return back to the very top of the reactor like this:


I have incorporated "Bleed" lines into both my DIY C02 Reactor and DIY Inline Heater Module. When I have to shut the system down for any reason--I use those Bleed lines to eliminate the air at system start-up that got into the Line from shutdown. I have been working on other things, but it won't take me long to plumb those Bleed lines back into the InFlow like the Diagram above. This will feed any C02 build-up right back into the system and does a wonderful job on my In-Tank powerhead Reactor:


The little C02 Venturi "Return" System does a wonderful job of returning the C02 back into the flow and the power C02 Reactor works much better because its just plain more efficient.

Basically, I am going to do it because I know it will make the reactor much more efficient---and I'm currently on DIY C02--so I can use all the help I can get....

[tazcrash69]

Originally Posted by banderbe

The pearling from my plants makes it look that way anyway

Barry, Is it possible that the pocket in the reactor is excess O2 being outgassed in the reactor? I used to get it (when it was overgrown with hornwort & other stems) in mine at the end of the day, and it would be gone by morning, only to start all over again.

Walter

[banderbe]

Originally Posted by Naja002

Basically, I am going to do it because I know it will make the reactor much more efficient---and I'm currently on DIY C02--so I can use all the help I can get....

Dumb question I'm sure, but what makes the CO2 go back up the venturi tube into the flow of water?

Also, how can you tell where the air pocket ends? Feeding CO2 back into a pocket of CO2 wouldn't help much

[Naja002]

what makes the CO2 go back up the venturi tube into the flow of water?

The Flow of water through the powerhead creates a suction or "draw"--that's how the venturi "draws" air down when it is used as originally designed on powerheads. Additionally, the gas will rise naturally, so with the draw plus natural tendency--it works without a hitch.

The flow going through the InFlow of your DIY Reactor should create the same draw/suction and it should work the same. Try it with clear tubing and you will see the bubbles being drawn back into the system--Flow.

how can you tell where the air pocket ends? Feeding CO2 back into a pocket of CO2 wouldn't help much

It feeds it back into the Flow to be resisted again and further dissolved. Any C02 that makes it back to "the Pocket" will just run through the venturi and back into the flow. The Venturi just recycles the C02 that has managed to get out of the flow and puts it back into the flow. Its Very efficient and forces your DIY Reactor to dissolve maximum C02.

Also, in the pic above, if you notice--the blue airline coupling that is stuck through the top of the tube is cut at an angle--that reduces the "Available" space for a pocket to form.