Material for CO2 tubing? - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 01-22-2008, 03:49 AM Thread Starter
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Material for CO2 tubing?

What is the recommended material for CO2 tubing? I'm having trouble with my DIY system because all the air line I have is pretty old vinyl tube and it seems that it's leaking. I currently have two short pieces that work okay but a few weeks ago the CO2 decided it could find an easier way out of the tube than through the end, unfortunately it was at about the same time my niece decided to dump a whole bottle of food into the aquarium in the middle of the night to "feed" the fish. I had a huge algae bloom that took a while to recover from but I did daily water changes for a couple weeks and I'm putting so much CO2 into my little 10G tank I'm sure the plants think I went pressurized (I've got 2x 2 liter bottles, I get about 30 bubbles per minute)

I'm afraid this tube will degrade pretty soon and I'll end up in bad shape again. So what material is recommended for a CO2 proof tubing? I have some sources where I can get tubing at a pretty good discount using the corporate account at work but I don't want to spend $.50/ft for PET-G (the same stuff soda bottles are made out of) if something like polyethylene works just as well, it's only $.04/ft and comes in a rainbow of colors. What's best and what's good enough for government work? I could also get Kynar, Tygon or Teflon but it starts getting really expensive, for this application I don't need medical grade so I'd like to stay away from the specialty plastics.
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post #2 of 9 (permalink) Old 01-22-2008, 04:19 AM
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I think it's urethane/polyurethane.

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post #3 of 9 (permalink) Old 01-22-2008, 06:34 AM
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http://www.rexgrigg.com

70 cents a foot, I think.

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post #4 of 9 (permalink) Old 01-22-2008, 07:44 AM
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Check this site out. The smaller the number on the co2 column the better.
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post #5 of 9 (permalink) Old 01-22-2008, 02:53 PM Thread Starter
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Quote:
Originally Posted by fishscale View Post
http://www.rexgrigg.com

70 cents a foot, I think.

I'd seen the tubing from Rex, I was hoping I could find something cheaper like polyethylene. The essence of DIY is finding an easily available substitute with a lower cost than the brand name or store bought solution that has equal or marginally worse performance.

It looks like PVC would be a good substitute but it's hard to tell the difference between PVC and Vinyl, as they're the same material but vinyl has plasticizers according to the chart posted by nokturnalkid the difference is pretty significant once the plasticizers are added. I could save at least 50 cents a foot and buy PVC, but it may or may not have plasticizers in it.

I'll contact Rex, I'm not sure where in Portland he is, if it's not too far out of my way I can pick it up direct and save a few dollars on shipping so the cost won't be too outrageous, it's not like I need 100 feet.
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post #6 of 9 (permalink) Old 10-19-2012, 07:30 AM
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Old thread but helpful info.
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post #7 of 9 (permalink) Old 10-19-2012, 04:06 PM
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urethane/polyurethane is the best it does not break down under exposure to CO2 and CO2 is not permeable through it.


Silicone tubing which is much cheaper and more readily available does not break down wit CO2 exposure but does have some degree of CO2 permeability. Hoppy attempted to test and quantify this at some point in the past and was not able to because the losses he was seeing were not measurable IIRC.

Long story short always used to urethane online and get it shipped, after reading Hoppy's experiment, just went out and bought some silicone and haven;t noticed any difference. One Disclaimer is I am not running a high psi atomizer which could certainly increase losses through the silicone.
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post #8 of 9 (permalink) Old 10-19-2012, 06:51 PM
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The problem with the table that shows how bad silicone is for containing CO2, is that it doesn't make it obvious that even the worst of the materials is still very good for containing CO2. Once a tubing type is good enough for our needs it makes no difference if another type is better - both are very good. I use whatever tubing I have or can get cheaply. Vinyl works fine, but does harden in time. Silicone works fine, but eventually hardens. "CO2 tubing" is hardest to use because it is so thick and rigid it takes effort to force it over a hose barb, and even more effort to remove it, but it probably lasts the longest without getting too hard.

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post #9 of 9 (permalink) Old 10-19-2012, 08:25 PM
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thanks for clarifying Hoppy. I didn't realize silicone would eventually harden as well. 5 months of exposure and mine is still quite supple, but I will keep an eye on it.

Thanks again.
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