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If you have connected your tubing securely and have checked for leakage in the joints (by spraying soapy water), the amount of CO2 leak would be negligible money wise. A lot of CO2 is also released on the water surface. :)
 

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if you can find it, use lee's elite airline tubing, the clear green one. it is safe from the effects of ozone and uv. i emailed them and they said it's made from pvc. i suspect that their black "stealth" tubing is also pvc. check that permeability chart and pvc is right up there with tygon. cheap, 20 ft for ~ $4. don't pay more for that "co2" tubing.
 

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I don't use the Tygon CO2 tubing either. I just use plain airline tubing (I believe it is polyvinyl) or the silicone stuff.

Some people will say that the silicone loses CO2 more quickly due to its increased permeability to CO2, but the amount lost is negligible.
 

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...Some people will say that the silicone loses CO2 more quickly due to its increased permeability to CO2, but the amount lost is negligible.
I read an article on Tom Barr's site that said the permeability of any tubing at the low pressure's we use is so small as to make any CO2 loss practically nonexistent. The permeability rates quoted from the tables that we occasionally see posted or linked are for high pressure.
 

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the permeability of the tubing does not change with pressure since it's a characteristics of the material. the diffusion rate clearly changes as a function of pressure. also, what's important is the gradient of partial pressures. on one side of the interface is 'pure' CO2, while the ambient air on the other side has a CO2 composition of a fraction of a percent (say 0.04%). so if you were running your CO2 at 1 bar (or roughly atmospheric pressure at sea level), you are still going to have a gradient across the interface. the gradient of partial pressures is what results in the CO2 loss.
 

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the permeability of the tubing does not change with pressure since it's a characteristics of the material. the diffusion rate clearly changes as a function of pressure. also, what's important is the gradient of partial pressures. on one side of the interface is 'pure' CO2, while the ambient air on the other side has a CO2 composition of a fraction of a percent (say 0.04%). so if you were running your CO2 at 1 bar (or roughly atmospheric pressure at sea level), you are still going to have a gradient across the interface. the gradient of partial pressures is what results in the CO2 loss.
I'll take one for the team and show my stupidity :) . In practical terms this means?
 

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the permeability of the tubing does not change with pressure since it's a characteristics of the material. the diffusion rate clearly changes as a function of pressure. also, what's important is the gradient of partial pressures. on one side of the interface is 'pure' CO2, while the ambient air on the other side has a CO2 composition of a fraction of a percent (say 0.04%). so if you were running your CO2 at 1 bar (or roughly atmospheric pressure at sea level), you are still going to have a gradient across the interface. the gradient of partial pressures is what results in the CO2 loss.
I'll take one for the team and show my stupidity :) . In practical terms this means?

It means this: ;)

I read an article on Tom Barr's site that said the permeability of any tubing at the low pressure's we use is so small as to make any CO2 loss practically nonexistent. The permeability rates quoted from the tables that we occasionally see posted or linked are for high pressure.
 

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the permeability of the tubing does not change with pressure since it's a characteristics of the material. the diffusion rate clearly changes as a function of pressure. also, what's important is the gradient of partial pressures. on one side of the interface is 'pure' CO2, while the ambient air on the other side has a CO2 composition of a fraction of a percent (say 0.04%). so if you were running your CO2 at 1 bar (or roughly atmospheric pressure at sea level), you are still going to have a gradient across the interface. the gradient of partial pressures is what results in the CO2 loss.
I think he means if you have a permeable piping, higher pressure = more leakage. Very little pressure = very little or no leakage. I would use skill like that to write instruction manuals.
 
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