DIY CO2 Inline Reactor

Discussion in 'D.I.Y.' started by dart, Apr 10, 2007.

  1. dart
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    dart Green fingers

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    I decided to start using CO2 in my new tank. After quite a bit of searching I found what looks to be a very good inline CO2 reactor (See: http://rexgrigg.com/diy-reactor.htm and http://www.plantedtank.net/forums/diy/22296-rex-reactor.html). Essentially the CO2 is fed into a tube from the return from a canister filter/sump.

    I made a simple version this weekend. I managed to find all the parts I needed at builders (despite their best efforts to convince me that they did not have what I needed). Below are the pics of the parts and the built unit (the CO2 inlet pipe is not shown "“ it is on the end opposite the T-piece).

    [​IMG]
    [​IMG]

    I used 50mm PVC pipe, 1 T-piece (I should have used an elbow instead...), 50mm threaded PVC converter and threaded nylon end caps.

    I tried it last night and unfortunately it leaks... I assumed that I would not have to glue the end caps on. I guess I was wrong :'(. I'm not sure if you can use PVC glue on the nylon threaded end-caps. So I’ll probably go with silicone. Hopefully this will do the trick.

    I noticed that the CO2 pressure would need to be reasonably high to force CO2 into the pipe i.e. against the pressure of the pump. I have a check value on the pipe to stop the pump forcing water into the CO2 yeast mix.

    Has anyone else used on of these? Any comments or suggestions?


    Thanks

    Andre
     
  2. HellRaiser
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    HellRaiser Algae harvester

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    Have you considered the method of using a gravel cleaner and powerhead combo to force react the CO2? From my CO2 testers apearance it works extremely fast and efficiant, ie the color changes from blue to green withing an hour or so after a 25% water change...
     
  3. HellRaiser
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    HellRaiser Algae harvester

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    And the only big reason i wont make a reactor operate near a canister filter is that especialy on the fluval i use you run the risk of causing an airlock in the filter if the CO2 gas builds up under the motor impeller.... And an airlock burn out of the filter means your waranty is void and you must pay for the repairs yourself...
     
  4. dart
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    dart Green fingers

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    I did see that design but I thought this would be easier as I did not need a second pump or something else in my tank (no sump at the moment :( )

    I don't think that would be an issue with this reactor as it should be placed on the return line. I.e. the water is pumped out of the canister and into the reactor. So any bubbles that do escape will end up in the tank and not the canister.

    I've never used a fluval so perhaps I misunderstand how it works...?
     
  5. R.C.
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    R.C. Moderator Staff Member

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    In-line reactors work great and best of all is that you can hide it out of sight.

    Rex Grigg has had great results with this reactor and is generally very highly spoken of by others.
     
  6. HellRaiser
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    HellRaiser Algae harvester

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    That sounds like a good idea to put it into the ouflow from the canister,just as long as it doesnt cause too much back pressere,that could strain the canister's pump if i remember correctly...Im no expert, just giving my own opinion from experience...
     
  7. dart
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    dart Green fingers

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    I don't think it would... There is no media in the tube and my elbow-joints are the same size as the outlet pipe. So there should not be much, if any, increase in the back pressure.

    Opinions are good, thanks :)
     
  8. HellRaiser
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    HellRaiser Algae harvester

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    I guess im just a clean water fanatic,so if i can get the little filter to run the reactor and do sum cleaning im happy... haha
    ill have a look at my fluval's setup and give your design a go,just let me know how you sort out that leak?
     
  9. kevinw
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    kevinw Noob

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    Can't you use plumbing tape for the joins?
    That should help.
     
  10. dart
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    dart Green fingers

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    I was just about to post saying that I was going to use plumbers tape :) Thanks. I might use silicone as well on the ends just to be sure. I'm not shy about overdoing things ;-)

    I'll let you know if it works.


    BTW what do you do about the difference between the pH when changing water? My tap water has a pH of about 8.x and I need to get it to about a pH of 7 for 15ppm CO[sub]2[/sub]. That is quite a big difference, will the difference be a problem for my fish if I change 30-50% of my water?
     
  11. HellRaiser
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    HellRaiser Algae harvester

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    Well,i use tap water that has aged for a week with bacteria and air bubbling through it,id say by the time i use it in the tanks the pH difference isnt too much,my fish havent complained yet :-D
     
  12. dart
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    dart Green fingers

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    I forgot to say that there is quite a lot of pressure on the airline tubing that feeds the CO[sub]2[/sub] into the reactor. I imagine that the yeast mix will generate enough CO[sub]2[/sub] to overcome this though. I can with a little effort blow air through the tube, given that I've heard that the yeast containers can explode if blocked there should be enough pressure...

    Don't forget that the water flows top - down, see the links I posted above.

    Finally I saw some good advice saying that when you change the yeast mix you should try not to loose pressure in the tubes etc. I.E. I've got an airline valve that I'll close when I change the yeast bottle. This should get things started quicker.

    Andre
     
  13. HellRaiser
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    HellRaiser Algae harvester

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    Just remember,with the yeast method you can only use plastic parts and valves...Any metal in contact with the CO2 will corrode due to carbonic acids produced with the yeast CO2....In other words the yeast method is a wet method, whereas pressurised CO2 from a canister is a dry method,meaning with them you can use any metal components...
     
  14. Henkt
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    Henkt Noob

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    I built my own variation of an inline reactor from PVC pipe - see the attached pics for a component breakdown. The PVC pipe is filled with a gazillion bio-balls to provide a complex path for the water/CO2 mixture inside the reactor. I chose a design where the pipe stands rather than lies on its side, due to space constraints and the layout of my tanks. In this configuration you can quite easily hide the pipe behind something since both inlet and outlet pipes are fitted on one side only.

    I inject pressurized CO2 straight into the inlet of my sump pump, with the CO2 line very close to the impeller, which then chops the CO2 up into a very fine mist. The reactor is mounted between the outlet of the pump and the spraybar return to the tank.

    I achieve pretty much a 100% dissoved CO2 rate through this reactor and the principle of operation is as follows:

    The water/gas mix is pumped into the top centre of the tube, where it hits the bio-balls and is forced down towards the bottom by the incoming stream of water. While the bubbles in the mix will attempt to float up, the flow of the water will continue to force it back down through the bio-balls until it eventually dissolves. I built several prototypes prior to my final model out of gravel vacuums so that I could observe the gas bubbles performing under various conditions. The reactor works just as well if CO2 is injected via airline into the reactor - typically you would push the airline some ways down into the tube and bubble up from below. The dissolved gas/water mix is picked up with an outlet pipe that goes to the bottom of the unit and is perforated for about 2cm at the bottom (see pics). Having the gas chopped up by the pump impeller has just resulted in the fastest change in pH, hence me settling on that as the working option.

    My final model is a litlle OTT (like everything else I do, my wife says) and is made from 110mm PVC pipe, with a screw-on end cap so that the unit can be opened and cleaned (which I do once every 6 months or so only). The hard (grey) PVC fittings are a bit more expensive, but well worth it, since they provide weight at the bottom so the unit can stand on its own.

    Having a bigger reactor makes for a nice buffer-effect once the CO2 solenoid shuts off, since there is obviously a nice volume of CO2 mixed in the unit, so the pH is maintained significantly longer than with smaller units.

    I hope the pictures are self-explanatory, but shout if anything is unclear.

    PS. I ran pressurized CO2 straight into my Fluval 404's inlet pipe for months and other than burping out a few big bubbles every now and again there was never a hint of an airlock... it is actually propably the next best thing to a reactor, since the Fluval acts as a big reactor - where do you think I got my idea for this design from ????   ;D

    Peace,
    Henkt
     
  15. HellRaiser
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    HellRaiser Algae harvester

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    Nice one henkt! That design has me interested in trying it myself! Ill try replicating it on autocad to establish the parts ill need to source from builders warehouse... Will be in a while though, or once i see my current system looses efficiency...
     
  16. ivansa
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    ivansa Algae harvester

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    A kiekie is worth a thousand words.

    Thanks

    Henk
     
  17. dart
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    dart Green fingers

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    Plumbers tape and silicone seems to have fixed the leak. It took quite a bit of plumbers tape nearly two-thirds of a roll per joint. The fittings are far from snug.... But it seems to be perfect now.

    I'm still a bit worried about the amount of pressure that the yeast mix needs to generate to overcome the pressure of the pump. I'm busy testing it at the moment. I'll know if it works soon.
     
  18. HellRaiser
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    HellRaiser Algae harvester

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    Great,please keep us posted with your results and solutions
     
  19. dart
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    dart Green fingers

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    I've decided to go with an in-tank rector instead of the "Rex Reactor" for now. I did make one small change to the design though (this is DIY after all :) ). Instead of installing a separate powerhead I'm using the return from my canister filter to power the reactor.

    Here is a pic of the reactor
    [​IMG]

    And a schematic
    [​IMG]

    The water from the canister filter (F) is pumped into the reactor. I control the flow rate into the reactor by using the two taps (A and B). The CO2 is fed into the reactor via tube (E) and into the air-stone. I've added a few bio-balls into the reactor to churn the water some more.

    The canister filter input (G) is on the opposite side of the tank so there should be enough circulation to evenly distribute the CO2.

    So far this is working fantastically. With between 2.5 and 3.5 bubbles per second (depending on time of the day) my pH dropped from 8.2 to about 7.2. So it seems to be pretty effective.


    Thanks for all the advice everyone.



    BTW how are you all creating the tops for the coke bottles?
    I've used rigid tubing from an old under-gravel filter. I've then drilled a hole in the bottle top (and the lining) and pushed the pipe through. I've silicone both sides and used plumbers tape on the thread. I then taped over the tops and pipe connections using insulation tape. I know its overkill but it works :)

    Any other ideas?

    Here is my current setup showing the three yeast bottles, gas separator and bubble counter
    [​IMG]
     
  20. kevinw
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    kevinw Noob

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    Looks good! There's just something about a good DIY project! :thumb:

    I do the bottle tops as follows:
    Drill a hole in the cap which is a bit smaller than the tubing; then I put the tubing in hot water (so its nice and soft) and then push it through the hole (this can require a little patience!). when the tubing cools it sits pretty snug. then i cover the top with prestik - and hey presto (!) there it is!
     

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