# will any tubing do for co2



## Deano3 (10 Nov 2013)

Hi quick question I have been having a slight problem and need to run a 6mm internal diameter pipe from regulator to a 6-4mm reducer and into the normal 4mm pipe only be a small length of 6mm but could I use any 6mm pipe or does it need to be co2 proof

Thanks dean


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## Deano3 (11 Nov 2013)

Anyone ? 



Thanks Dean


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## ian_m (11 Nov 2013)

Yes needs to be CO2 proof as CO2 will "dissolve" in most common rubbers/plastics either making is melt or harden.


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## Rich Jackson (11 Nov 2013)

I always though it needed to be co2 proof.


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## sa80mark (11 Nov 2013)

Just replied on your other post 

I think im right in saying it needs to be Polyurethane


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## foxfish (11 Nov 2013)

I don't doubt that using proper C02 tubing is the right way to go however I have always used silicone air line!
After about  7-8 mounths of use the silicone starts to harden & I then replace it.
I don't use high pressure devices though as I run my reactor at under one bar.


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## parotet (11 Nov 2013)

Is it just a matter of pressure? Even with DIY yeast CO2 systems it is recomended to use co2 proof tubing...


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## sa80mark (11 Nov 2013)

When researching regulators for when I build mine I came across a post that stats silicone tube shouldn't be used as its leaks co2, depending on the pressure it was anywhere from 5% - 20% it didnt explain anything in more detail so im not sure how accurate the figures or even the info,

Mark


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## foxfish (11 Nov 2013)

Oh! perhaps we shouldn't use silicone to hold our tanks together then?


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## parotet (11 Nov 2013)

Well, the pressure and amount of CO2 on the tube has nothing to do with the pressure and amount of CO2 in the water...


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## three-fingers (11 Nov 2013)

foxfish said:


> Oh! perhaps we shouldn't use silicone to hold our tanks together then?


Our tanks contain water not CO2.  The two compounds have different chemical properties and thus interact with silicone differently .


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## GHNelson (11 Nov 2013)

foxfish said:


> Oh! perhaps we shouldn't use silicone to hold our tanks together then?


Depends what silicone you use.
hoggie


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## foxfish (11 Nov 2013)

LOL some of you guys are just toooo serious 

Like I said C02 tubing is the way to go OK!

However I have been using C02 for around 30 years & never once ever had a problem using silicone tubing due to it leaking or deteriorating.... I have had bubble counters explode, watched my airline expand using high pressure atomisers but never seen it fail!   

I don't recommend using anything other than C02 tubing... just pointing out a fact based on my own experience!


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## parotet (11 Nov 2013)

Veeeery serious   ;-P


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## parotet (12 Nov 2013)

Last night I spent quite a lot of time reading about this and I think, if what I read is not wrong, that a good co2 tubing has to maintain its shape, has to be inert (no reaction to co2) and should be flexible.

 It seems that silicone tubing meets all this, but you can find people that have used this material without reporting any problem and other people say that co2 leaks in this tubing. Who knows... No one measures the co2 diffused. Air tubing is said not the right one, don't know the material but probably silicone also or other plastics (some of them cheap and smelly).

The only material with which everyone agree to be perfect is polyethylene, sold as co2 tubing in local pet shops.
In my town both tubing can be found very cheap in specialized plastic shops, in the length you want and in a wide range of diameters.. At least 3 times cheaper than in local pet shops.


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## parotet (12 Nov 2013)

Much more serious information than mine... Nice list of all the tubing materials and the permeability to CO2 and other products:
http://www.coleparmer.com/TechLibraryArticle/700]*Tubing selection guide*[/url]


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## parotet (12 Nov 2013)

ups... ugly link!


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## ian_m (12 Nov 2013)

Technical Resource Library from Cole-Parmer 

Well this shows why silicone should not be used, it has one of the highest CO2 permeabilities of all the tubing they feature -> 20,132 cm3.cm/cm2.cm-hg x10-10 (that's cubic cm x cm thickness / cm area x cm mercury pressure).

I think the silicone hardens with CO2.

Polyethylene, polypropylene, polyurethane  and PVC all have non zero values.

However PVC hardens in presence of CO2 absorption, so I suspect polyurethane is the probably best of the bunch in that yes it absorbs CO2 but doesn't soften or harden like other plastics.

Also a quick check of 4mm PVC hosing (rswww.com) max working pressure of 4bar, which doesn't leave much margin of safety with regulator running at say 2bar. Where as similar polyurethane is rated 20bar and silicone at 75bar (but 270% elongation !!!).

So looks like polyurethane tubing is best of the bunch for CO2.


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