# Diy----- Co2-----with Reservoir?



## essabee (Oct 11, 2006)

Can I build a DIY CO2 system with a reservoir and a solenoid valve? The valve would stop the CO2 from going to the aquarium at lights off stage, instead direct the CO2 flow into a water displacement float tank connected to the CO2 pipe via a T on the production side of the valve.


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## Dewmazz (Sep 6, 2005)

I wouldn't advise it. Because yeast bottles continually build pressure, you'd need to do some clever calculations based on how much co2 is produced vs. how much the bottle can hold before it blows. You may also run into problems releasing the gas from the resivoir. The gas wouldn't empty by itself if the pressure continues from the yeast bottle (see fig). You'd need a release valve when gas isn't being poured into the resivior. In addition, you'd need 2 soleniods. Gas takes the path of least resistance. Unless you capped off the resivior, it'd probably fill up berfore your method of diffusion (diffuser, reactor, etc.). Sorry to burst your bubble.


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## hoppycalif (Apr 7, 2005)

If you had a big enough reservoir, actually an accumulator, to hold a day's worth of CO2 production, and maybe even more, this could work. The accumulator would have to be designed to maintain a pressure of about 1 to 2 psi, no matter how much or how little CO2 was in it. Something like a big bellows with a small weight on top would do it. I suspect a pressurized CO2 system would end up looking economical if you try this.


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## John N. (Dec 11, 2005)

Great Pictorial Dewmazz, and I agree an exploding reservoir is waiting to happen. 

Are you trying to prevent CO2 entering your tank during lights out? If so, why not keep simple and run an airstone at night to outgas any CO2. OR you could keep the system hooked up to a solenoid, and have it turn on at night to let the gas deflate into the open air..no reservior.

-John N.


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## TonyV2 (Oct 16, 2006)

The other thing to consider, assuming it doesn’t blow up, :shock: is that in the morning when you open the valve you will have a flood of CO2 that I think cause the Ph to plummet. :flame: 

When I started my DIY CO2 setup I used a diffuser with a powerhead. At night I would just turn the powerhead off. The CO2 would still bubble into the tank but just disperse at the top with little absorption. In the morning I would turn it back on.

I now just let it go 24/7 with no problem.


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## essabee (Oct 11, 2006)

I don’t know how to post a diagram! So let me try a word picture.

The reservoir would be like an upturned open bucket. The inlet/outlet is a single pipe fitted to the normal bottom of the bucket (when upturned it now on the top). Along the collar of the bucket, use a molded lead rod having the desired weight for the pressure desired. When upturned the collar is at the bottom. Now put this upturned bucket in a let us say an empty 20 liter drum so that the entire bucket is submerged when you fill it up with water. Open the inlet/outlet valve, the inside of the upturned bucket is now filled with water.

When the supply side solenoid is closed during light off time, CO2 would displace the water inside the upturned bucket. If the volume of the CO2 produced during this closed time is greater than the reservoir can hold, it would merely escape, bubbling out from under the upturned bucket. No explosion waiting to happen. Very simple, very low cost, a couple of empty containers, a T, CO2 pipe, some scrap lead melted into a bar and hammer molded.


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## Dewmazz (Sep 6, 2005)

Go for it. Worst that can happen is you lose a few $ on supplies and/or a bucket with some lead stuck to it .


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## essabee (Oct 11, 2006)

Will someone tell me if a solenoid valve can be set to controll the CO2 flow when the CO2 is at a constant pressure.

Does anyone have any detail of the pressure handling capacity of areated drink 2l pet bottle.


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## JPeeps (Nov 2, 2006)

I use this brass valve for my co2.http://us.st11.yimg.com/us.st.yimg.com/I/worldpets_1923_161655010
I picked it up at petsmart.The left inlet comes with a tiny screw type plug,I left it on and I use the right inlet and only one outlet.That way when you need to turn off the co2,just close the outlet for the tank,and open the other one,vice-versa for when you turn the lights on.That way you have no pressure build-ups.


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## essabee (Oct 11, 2006)

For that purpose I only need a stopcock. 

What actually I need is a solenoid which can be opened and closed electrically, but which I can also set a fixed flow rate so that every time I start the flow the rate of flow remains a constant, especially when my CO2 would be at a costant pressure.


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## schaadrak (Aug 18, 2006)

You're best bet is to put a needle valve just after your solenoid. It'll be easier to find than a special solenoid/regulator combo.

Great idea on the accumulator bucket, BTW. I'm also working out the plans for a pressurized DIY system (still checking material prices too see if its economically feasible compared to a commercial system) so I'll definitely be following this thread. Keep us posted.

EDIT: Also, the psi limit for a standard 2L soda bottle is around 100 psi. We used to blow them up by connecting them to the air hoses in the shop I worked at, and the tire pressure gauge got to about a hundred each time they blew.


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## hoppycalif (Apr 7, 2005)

Water will hold about 1000 or more ppm of CO2 in solution at normal temperatures and pressures. So, one effect of this storage method is to create a drum or barrel of very high CO2 ppm water. Possibly you could add enough baking soda and GH booster to that water to make it harder for CO2 to dissolve in the water (if that actually works). Otherwise a lot of the stored CO2 will be stored in the water, not as a gas above the water. Remember, the water will reach an equilibrium with the CO2 in the air above the water, and that air will be mostly CO2.

Now that I think a bit more, if any of that water is exposed to the outside air, the CO2 will just be lost, by moving to the water in the bucket, to the water in the drum, to the outside air.


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## essabee (Oct 11, 2006)

hoppycalif said:


> Water will hold about 1000 or more ppm of CO2 in solution at normal temperatures and pressures. So, one effect of this storage method is to create a drum or barrel of very high CO2 ppm water. Possibly you could add enough baking soda and GH booster to that water to make it harder for CO2 to dissolve in the water (if that actually works). Otherwise a lot of the stored CO2 will be stored in the water, not as a gas above the water. Remember, the water will reach an equilibrium with the CO2 in the air above the water, and that air will be mostly CO2.
> 
> Now that I think a bit more, if any of that water is exposed to the outside air, the CO2 will just be lost, by moving to the water in the bucket, to the water in the drum, to the outside air.


What if I replace the water in the tank/drum with either oil or water topped with a, say an inch of oil.

Variation only the external water in the drum with a inch of oil.

Saturation one time only, no connection to atmosphere! No losses from escapes by diffusion or futher dissolution.


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## hoppycalif (Apr 7, 2005)

essabee said:


> What if I replace the water in the tank/drum with either oil or water topped with a, say an inch of oil.
> 
> Variation only the external water in the drum with a inch of oil.
> 
> Saturation one time only, no connection to atmosphere! No losses from escapes by diffusion or futher dissolution.


It would depend on whether or not CO2 dissolves into oil. I have no idea if it does. Nor do I know how one would measure it. If it doesn't, then the idea should work, leaving you with, in effect, seltzer water topped by oil in the drum and seltzer water in the bucket, with CO2 above the water.

Edit: I found a reference: www.jbc.org/cgi/reprint/72/2/545.pdf , which shows that CO2 does dissolve into mineral oil, but that the CO2 moves thru the oil very slowly, so your oil "cap" idea should work very well.


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## rodmarquezjr (Jul 16, 2006)

A water displacement seal wouldn't work. CO2 is highly soluble in water. I tried this once: I filled upturned plastic bottles with CO2 while the open end was submerged underwater. I capped it with a little water inside to prevent the gas from leaking out through the cap. After a few days, the plastic bottle collapsed inward due to a partial vacuum created when the water absorded the CO2. I couldn't open the cap anymore as well due to the partial vacuum.


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