The same problem arises over and over again when using a DIY Co2 type system. Trying to figure out a way to shut off the Co2 at night and accurately regulating the amount of Co2 coming from the system. I use a reservoir 2L bottle topped with a 3-way manifold to accomplish this. One opening is for a brass barb for gas entering, one is for a ball valve to turn on/off gas flow to the tank, and one is for a safety release valve set at 60psi. To fine tune the flow I added a brass valve to the tubing a few inches down the line. Use thread sealant everywhere you can and apply silicon between check valves and tubing as there will be pressure built up over night. I've been running this for a few months and haven't had any accidents or disconnects.
First, lets talk about the power plant. I've used K1-V1116 wine yeast mainly because of its high alcohol tolerance, low flocculation, and general hardiness. It's worked great. The usual 2 cups of water, 2 cups of sugar, 1/2 teaspoon of yeast works strong for about 30 days or so.
Here's the setup
2L Bottle cap with thread sealant. This is so the manifold can be seated on the bottle cap.
At night I close the ball valve. According to mythbuster's, 2L bottles will burst at 90psi, so I chose a 60psi safety valve. Gas is allowed to build up over night in the 2L bottle. The safety valve has never gone off. Once opened I have the brass needle valve to reduce the flow down to one or two bubbles per second.
A word to the wise, these types of diffusers make a subtle chirping sound
Very interesting! Since the objections to pressurized CO2 systems are usually related to the high initial cost, how much did this setup cost? When it is time to replace the yeast sugar mixture do you run a risk of trying to open a bottle that is now pressurized, or has the pressure gone down by then?
Thanks Hoppy & xmas_one! The total setup cost $42 excluding the diffuser and bubble counter assuming you'd need that with a pressurized system also. But ya, the second I got finished with this I thought to myself, damn, I should have just gotten that regulator w/solenoid for my paintball tank from aquariumguys for $80. No problems with pressure release when switching bottles, most likely because the yeast is pretty much spent.
It looks like the relief valve has a manual pull, so if you ever do need to take your reactor off when it's pressurized, all you need to do is pull the ring on the valve to relieve the pressure. Nicely done! I thought about using a balloon for overnight "storage" but was scared of the possible mess.
I would very much like to give this a try, but the only place I can find one of these safety valves is on evil-bay and the only seller that ships to me has got only 35psi and 75psi ones. Which would you recommend? I'm trying to build up enough pressure to activate an inline atomizer, can someone tell me what is the typical psi those compressed co2 tanks are usually run at(ie the meter valve readings)?
Ya, a needle valve isn't really made for holding pressure, that's why you need the ball valve. And the ball valve isn't really good at making precise adjustments to the flow of CO2, that's why you need the needle valve. Good luck with it!
Coke bottles are made from Polyethylene Terephthalate (PET), a material that is inherently good at resisting acids (carbonic acid is a weak acid from co2). There's a reason why carbonated beverages are stored in these bottles. I read a study on the diffusion of co2 through (PET) performed over a 2 year time period. The bottle didn't corrode over that time frame, although, amazingly 90% of co2 had escaped through the bottle walls by the end of that time frame.
I guess glass would've been a better container. Just look for signs of corrosion, like discoloration, and I wouldn't worry about the bottle degrading.
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