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will any tubing do for co2

Deano3

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8 Feb 2012
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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
 

ian_m

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

foxfish

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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.
 

sa80mark

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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
 

parotet

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

foxfish

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LOL some of you guys are just toooo serious :stop:

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!
 

parotet

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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.
 

ian_m

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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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