DIY Co2 problems....need recommendations

[zackish]

This is what my DIY Co2 top looks like. It's a simple brass barb you can buy in the plumbing section of home depot for $2.00. It worked for the first 3 weeks then all of a sudden when I made my new mixture the seal broke on the silicone so the Co2 in my bottle was just leaking through it.

This is the top of it, it is called a brass barb. The top/nipple of it is exactly the right size for my silicone tubing to fit over very tightly.
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This is what it looks like under the cap, this end is 1/4" threaded and I drilled the hole tight enough in the cap so it screwed in tightly. I also siliconed the whole inside of this and the threads on the barb.
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Any ideas of why all of a sudden the seal is breaking would be greatly appreciated. I have heard of some people doing it this way and it has worked really good. I may just try and poke a hole in a coke cap and silicone the tubing right into the cap.

Thanks in advance, Zac.

[Chrona]

The only thing I can think of is if you hit the tip of the barb on something hard enough to pop a thread in the cap. The setup is much sturdier than a traditional air tubing through the cap rig. Also, maybe the hole was a tad too large? I actually used a metric drill bit for a standard size brass barb and wiggled the bit until i got a hole size with a very tight fit (took a few caps). Also, for future reference, you don't need all of that silicone, as it really doesn't do much when it's globbed on there. Simply wipe everything with some rubbing alcohol, and coat the threads on the brass barb with some silicone and screw it in (after threading the cap). You can put a small bead on top, but it's not really neccesary.

Heck, gimme a couple of bucks and I'll make you one, lol.

[Dave66]

The Co2 eats through the silicone due to a chemical reaction. Use aquarium-grade five-minute epoxy to make your seals.

That reaction is why I have to replace the silicone tubing on my Co2 systems every month or so. I should add I use pressurized Co2.

Dave

[RobbieG]

I think Chrona's right about the hole (and everything else) - I'd just try again with a smaller hole.

[Chrona]

CO2 reacts with tubing fairly easily because it has such an immense area to do so. The area in between the brass barb and the hole in the cap is so miniscule that it would take forever for anything to happen, especially if you put in a bead of the stuff. Furthermore, CO2 doesn't eat silicone, it just makes it brittle and less able to contain the gas, but given such a tiny gap, the CO2 loss from the tubing itself would far surpass that from the cap connection. 100% silicone (in aquarium silicone) is remarkably resistant to most anything you can throw at it, save strong acids, as shown by the link at the bottom. I don't know for sure, but I would assume that silicone tubing is a mixture of silicone and other material, giving it desirable properties for tubing, but also making it more susceptible to brittling (if that's a word). The problem is the physical strength of his setup (which should not be a problem with a proper size hole), not the chemical resistance, imo.

As a side note, CO2 diffuses rather quickly through silicone tubing (Up to 6% per foot), which is why you should either use vinyl (the cheapest - but becomes brittle over time) or CO2 resistant tubing such as Tygon, or other tubing made especially for CO2 applications (though you should be careful that it's not actually silicone)

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Check out the permeability of silicone vs vinyl vs Tygon with regards to CO2.

[zackish]

As usuall....thanks for the help chrona. I am gunna try to reseal it, my barb screwed in pretty tight and I coated the threads thats why I was surprised it wasn't holding up. Especially since it held up for the first 3 weeks.

[Bill M.]

I have had nothiong but success with drilling a hole the size of the inside diameter of the tubing, cutting it at an angle, and pulling it through, and applying a coat of hot glue on both inside and out of the cap. You could try that. All together, my set up cost me .88 cents, becasue I had the yeast and airline tubing... just curious, whats your recipie?? Mine is 2 cups sugar and 1 tsp. yeast. I mix this in a measuring cup with the hottest water out of my tap, then pour it in my 1 L bottle, and fill it with the hottest water again to about 2 inches below the cap.... IDK why, but it always begins bubbleing within 30 mins, at a rate of 50-60 BPM, last about 1.5 weeks....

[DaleJr08]

Someone may have said this allready but, if you put the brass fitting under the bottle cap and put alittle silicone between the cap and the fitting the pressure inside the bottle should keep the system air tight. (sorry that was a long sentance there lol)