# DIY CO2 with solenoid valve



## jkh13 (Aug 5, 2014)

I recently purchased this DIY CO2 kit for a 36 litre tank.
(remove the space in ebay)
http://www.eb ay.co.uk/itm/Complete-DIY-CO2-generator-system-Kit-with-CO2-diffuser-planted-aquarium-/260794496171?pt=UK_Pet_Supplies_Fish&hash=item3cb89034ab


I wanted a way to shut off the CO2 supply during the night to avoid suffocating the fish in the tank and was thinking I would invest in a solenoid valve in order to do this. Seeing as it is not a good idea to block off the output of CO2 from the plastic bottles I was thinking the solenoid would switch the CO2 line to flow into the air instead of into the tank using a 3 way solenoid like this one:
(remove the space in ebay)
http://www.eb ay.co.uk/itm/1-4-DC-12V-3-way-2-position-Pneumatic-Electric-Solenoid-Valve-BSP-Air-Alu-Alloy-/321437559023?pt=LH_DefaultDomain_3&hash=item4ad72be8ef

At night a timer on the power would turn off the solenoid and switch the output of CO2 to go into the air instead of the water.

I was wondering if anyone has tried something like this before and also what sort of connectors I would need on the solenoid to fit the standard airlines to the inputs/outputs. Would something like this be suitable?
(remove the space in ebay)
http://www.eb ay.co.uk/itm/BSP-Male-1-4-6mm-Pack-4-Straight-Push-Pneumatic-Fitting-Stud-LOTS-/321495152651?pt=LH_DefaultDomain_3&hash=item4ada9ab80b


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## Daximus (Oct 19, 2011)

I'm not trying to rain on anyone's parade....but I'm unsure if this will work. The solenoid and venting to air is proper and feasible, but in my experience with DIY co2 it won't build enough pressure to achieve your goals. Meaning, the first time you purge to air the reactor will dump its pressure...it might be 6-8 hours before it creates the required pressure to again overcome line pressure and water displacement. You would have a heck of a time getting your co2 timed with your lights in my opinion.


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## jkh13 (Aug 5, 2014)

Daximus said:


> I'm not trying to rain on anyone's parade....but I'm unsure if this will work. The solenoid and venting to air is proper and feasible, but in my experience with DIY co2 it won't build enough pressure to achieve your goals. Meaning, the first time you purge to air the reactor will dump its pressure...it might be 6-8 hours before it creates the required pressure to again overcome line pressure and water displacement. You would have a heck of a time getting your co2 timed with your lights in my opinion.


Ah that's a good point that I hadn't considered actually. Perhaps it could work if inside of venting to air it went into another bottle filled with water with a diffuser at the bottom for the Co2 and a small hole at the top to release built up gas?


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## Daximus (Oct 19, 2011)

jkh13 said:


> Ah that's a good point that I hadn't considered actually. Perhaps it could work if inside of venting to air it went into another bottle filled with water with a diffuser at the bottom for the Co2 and a small hole at the top to release built up gas?


Definitely doable. The goal would be to maintain pressure in the reactor at all times. Sure, you'll have a dip when you switch outputs, but it shouldn't be as drastic as purging to air. 

I love tinkering and inventing...just don't chase the rabbit too hard. You can get a decent Co2 setup for a little over a $100. I know that's more than DIY...but time is money. :hihi:


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## oldpunk78 (Nov 1, 2008)

You could probably do something like put a 10psi cracking pressure check valve on the venting side to keep the pressure up. There are better ways, but there would be more cost involved.


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## jkh13 (Aug 5, 2014)

oldpunk78 said:


> You could probably do something like put a 10psi cracking pressure check valve on the venting side to keep the pressure up. There are better ways, but there would be more cost involved.


Double checking the kit I bought, it appears that it has a built in adjustable needle valve on the output of the second bottle. If I make the opening very small could this possibly be used to maintain pressure within the bottle?


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