Re:Silicone tubing and CO2

[George Booth <booth at frii_com>]

>Date: Sun, 19 Nov 2000 05:54:32 -0500
>From: "Wayne Jones" <waj at mnsi_net>
>
>Jean-Paul Chicheret has written an article, dated Jan. 7, 2000, in which he
>encourages us all to change our silicone tubing, which he says is far too
>permeable ("up to 30%"), for Tygon-brand tubing
>
>I reply:
>
>I have heard this repeated before but I don't buy it at all. Silicone tubing
>does harden a little bit over time but it lasts many years. I have tested
>the tubing by placing my yeast sugar system under water and clamping off the
>end of the silicone tubing line. There were no detectable leaks at all let
>alone a loss of 30% of the gas. In my test situation the silicone line was
>under considerable pressure too. In actual practice the pressure in the CO2
>line is vanishingly small or even negative. Perhaps silicone tubing leaks if
>it is under 40 psi pressure but it sure doesn't seem to at low presssures.

Being permeable and leaking are two different things. If CO2 was diffusing 
through the silicone tubing in your test setup, it would dissolve directly 
into the water - you won't see any bubbles. Also, I don't see how you could 
measure a loss of CO2 - 30% or otherwise.


George Booth in Ft. Collins, Colorado (booth at frii_com)
"The web site for Aquatic Gardeners by Aquatic Gardeners"
   http://www.frii.com/~booth/AquaticConcepts/

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